Make CBFS output more consistent

- Prefix all CBFS output messages with CBFS:
- Add an option DEBUG_CBFS that is off by default. Without DEBUG_CBFS
  enabled, the code will no longer print all the files it walks for
  every file lookup.
- Add DEBUG() macro next to LOG() and ERROR() to specify which messages
  should only be visible with DEBUG_CBFS printed.
- Actually print a message when the file we're looking for was found. :)

old:
Searching for fallback/coreboot_ram
Check cmos_layout.bin
Check pci8086,0106.rom
Check fallback/romstage
Check fallback/coreboot_ram

Change-Id: I2d731fae17a5f6ca51d435cfb7a58d6e017efa24
Stage: loading fallback/coreboot_ram @ 0x100000 (540672 bytes), entry @ 0x100000
Stage: done loading.
new:
CBFS: Looking for 'fallback/coreboot_ram'
CBFS: found.
CBFS: loading stage fallback/coreboot_ram @ 0x100000 (507904 bytes), entry @ 0x100000
CBFS: stage loaded.
Signed-off-by: Stefan Reinauer <reinauer@google.com>
Reviewed-on: http://review.coreboot.org/993
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/Kconfig

@@ -664,6 +664,13 @@ config GDB_STUB
 	  If enabled, you will be able to set breakpoints for gdb debugging.
 	  See src/arch/x86/lib/c_start.S for details.
 
+config DEBUG_CBFS
+	bool "Output verbose CBFS debug messages"
+	default n
+	depends on TPM
+	help
+	  This option enables additional CBFS related debug messages.
+
 config HAVE_DEBUG_RAM_SETUP
 	def_bool n