Extend CBFS to support arbitrary ROM source media.

Summary:
	Isolate CBFS underlying I/O to board/arch-specific implementations as
	"media stream", to allow loading and booting romstage on non-x86.

	CBFS functions now all take a new "media source" parameter; use
	CBFS_DEFAULT_MEDIA if you simply want to load from main firmware.
	API Changes:
		cbfs_find => cbfs_get_file.
		cbfs_find_file => cbfs_get_file_content.
		cbfs_get_file => cbfs_get_file_content with correct type.

CBFS used to work only on memory-mapped ROM (all x86). For platforms like ARM,
the ROM may come from USB, UART, or SPI -- any serial devices and not available
for memory mapping.

To support these devices (and allowing CBFS to read from multiple source
at the same time), CBFS operations are now virtual-ized into "cbfs_media".  To
simplify porting existing code, every media source must support both "reading
into pre-allocated memory (read)" and "read and return an allocated buffer
(map)". For devices without native memory-mapped ROM, "cbfs_simple_buffer*"
provides simple memory mapping simulation.

Every CBFS function now takes a cbfs_media* as parameter. CBFS_DEFAULT_MEDIA
is defined for CBFS functions to automatically initialize a per-board default
media (CBFS will internally calls init_default_cbfs_media).  Also revised CBFS
function names relying on memory mapped backend (ex, "cbfs_find" => actually
loads files). Now we only have two getters:
	struct cbfs_file *entry = cbfs_get_file(media, name);
	void *data = cbfs_get_file_content(CBFS_DEFAULT_MEDIA, name, type);

Test results:
 - Verified to work on x86/qemu.
 - Compiles on ARM, and follow up commit will provide working SPI driver.

Change-Id: Iac911ded25a6f2feffbf3101a81364625bb07746
Signed-off-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-on: http://review.coreboot.org/2182
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/device/oprom/realmode/x86.c

@@ -248,8 +248,9 @@ void vbe_set_graphics(void)
 #if CONFIG_BOOTSPLASH
 	struct jpeg_decdata *decdata;
 	decdata = malloc(sizeof(*decdata));
-	unsigned char *jpeg = cbfs_find_file("bootsplash.jpg",
-						CBFS_TYPE_BOOTSPLASH);
+	unsigned char *jpeg = cbfs_get_file_content(CBFS_DEFAULT_MEDIA,
+						    "bootsplash.jpg",
+						    CBFS_TYPE_BOOTSPLASH);
 	if (!jpeg) {
 		printk(BIOS_DEBUG, "VBE: No bootsplash found.\n");
 		return;
@@ -366,7 +367,8 @@ void do_vsmbios(void)
 	printk(BIOS_SPEW, "VSA: Real mode stub @%p: %d bytes\n", REALMODE_BASE,
 			(u32)&__realmode_code_size);
 
-	if ((unsigned int)cbfs_load_stage("vsa") != VSA2_ENTRY_POINT) {
+	if ((unsigned int)cbfs_load_stage(CBFS_DEFAULT_MEDIA, "vsa") !=
+	    VSA2_ENTRY_POINT) {
 		printk(BIOS_ERR, "Failed to load VSA.\n");
 		return;
 	}

src/device/oprom/yabel/vbe.c

@@ -725,7 +725,9 @@ void vbe_set_graphics(void)
 	 * cares. */
 	// int imagesize = 1024*768*2;
 
-	unsigned char *jpeg = cbfs_find_file("bootsplash.jpg", CBFS_TYPE_BOOTSPLASH);
+	unsigned char *jpeg = cbfs_get_file_content(CBFS_DEFAULT_MEDIA,
+						    "bootsplash.jpg",
+						    CBFS_TYPE_BOOTSPLASH);
 	if (!jpeg) {
 		DEBUG_PRINTF_VBE("Could not find bootsplash.jpg\n");
 		return;

src/device/pci_rom.c

@@ -35,7 +35,8 @@ struct rom_header *pci_rom_probe(struct device *dev)
 	struct pci_data *rom_data;
 
 	/* If it's in FLASH, then don't check device for ROM. */
-	rom_header = cbfs_load_optionrom(dev->vendor, dev->device, NULL);
+	rom_header = cbfs_load_optionrom(CBFS_DEFAULT_MEDIA, dev->vendor,
+					 dev->device, NULL);
 
 	u32 vendev = (dev->vendor << 16) | dev->device;
 	u32 mapped_vendev = vendev;
@@ -45,8 +46,10 @@ struct rom_header *pci_rom_probe(struct device *dev)
 
 	if (!rom_header) {
 		if (vendev != mapped_vendev) {
-			rom_header = cbfs_load_optionrom(mapped_vendev >> 16,
-					mapped_vendev & 0xffff , NULL);
+			rom_header = cbfs_load_optionrom(
+					CBFS_DEFAULT_MEDIA,
+					mapped_vendev >> 16,
+					mapped_vendev & 0xffff, NULL);
 		}
 	}