drivers/intel/gma, soc/intel/common: improve cooperation

Instead of both featuring their own VBT loaders, use a single one.
It's the compression-enabled one from soc/intel/common, but moved to
drivers/intel/gma.

The rationale (besides making all the Kconfig fluff easier) is that
drivers/intel/gma is used in some capacity on all platforms that load a
VBT, while soc/intel/common's VBT code is for use with FSP.

BUG=b:79365806
TEST=GOOGLE_FALCO and GOOGLE_CHELL both build, exercising both affected
code paths.

Change-Id: I8d149c8b480e457a4f3e947f46d49ab45c65ccdc
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://review.coreboot.org/26039
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/intel/common/vbt.c

@@ -21,48 +21,7 @@
 #include <bootstate.h>
 
 #include "vbt.h"
-
-#define VBT_SIGNATURE 0x54425624
-
-__weak
-const char *mainboard_vbt_filename(void)
-{
-	return "vbt.bin";
-}
-
-static char vbt_data[8 * KiB];
-static int vbt_data_used;
-
-void *locate_vbt(size_t *vbt_size)
-{
-	uint32_t vbtsig = 0;
-
-	if (vbt_data_used == 1)
-		return (void *)vbt_data;
-
-	const char *filename = mainboard_vbt_filename();
-
-	size_t file_size = cbfs_boot_load_file(filename,
-		vbt_data, sizeof(vbt_data), CBFS_TYPE_RAW);
-
-	if (file_size == 0)
-		return NULL;
-
-	if (vbt_size)
-		*vbt_size = file_size;
-
-	memcpy(&vbtsig, vbt_data, sizeof(vbtsig));
-	if (vbtsig != VBT_SIGNATURE) {
-		printk(BIOS_ERR, "Missing/invalid signature in VBT data file!\n");
-		return NULL;
-	}
-
-	printk(BIOS_INFO, "Found a VBT of %zu bytes after decompression\n",
-		file_size);
-	vbt_data_used = 1;
-
-	return (void *)vbt_data;
-}
+#include <drivers/intel/gma/opregion.h>
 
 void *vbt_get(void)
 {