RISCV: add this architecture to cbfstool

Change-Id: I6d972e595f12585cda08e1a6d2b94b4bf4f212f5
Signed-off-by: Ronald G. Minnich <rminnich@gmail.com>
Reviewed-on: http://review.coreboot.org/7067
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

util/cbfstool/cbfs.h

@@ -53,6 +53,7 @@ struct cbfs_header {
 #define CBFS_ARCHITECTURE_X86      0x00000001
 #define CBFS_ARCHITECTURE_ARM      0x00000010
 #define CBFS_ARCHITECTURE_AARCH64  0x0000aa64
+#define CBFS_ARCHITECTURE_RISCV    0xc001d0de
 
 #define CBFS_FILE_MAGIC "LARCHIVE"