cbfstool: Add cbfs_image new CBFS image manipulation API.

Current cbfstool implementation is relying on global variables to pass processed
data, and the calculation of address is based on x86 architecture (ex, always
assuming 0x0000 as invalid address), not easy to be used on platforms without
top-aligned memory mapping. This CL is a first step to start a new cbfstool
without global variables, and to prevent assuming memory layout in x86 mode.

The first published APIs are for reading and writing existing CBFS ROM image
files (and to find file entries in a ROM file).

Read cbfs_image.h for detail usage of each API function.

Change-Id: I28c737c8f290e51332119188248ac9e28042024c
Signed-off-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-on: http://review.coreboot.org/2194
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

util/cbfstool/cbfs.h

@@ -42,6 +42,8 @@ struct cbfs_header {
 #define CBFS_ARCHITECTURE_X86      0x00000001
 #define CBFS_ARCHITECTURE_ARMV7    0x00000010
 
+#define CBFS_FILE_MAGIC "LARCHIVE"
+
 struct cbfs_file {
 	uint8_t magic[8];
 	uint32_t len;