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/common.c

@@ -132,6 +132,7 @@ static struct {
 } arch_names[] = {
 	{ CBFS_ARCHITECTURE_AARCH64, "arm64" },
 	{ CBFS_ARCHITECTURE_ARM, "arm" },
+	{ CBFS_ARCHITECTURE_RISCV, "riscv" },
 	{ CBFS_ARCHITECTURE_X86, "x86" },
 	{ CBFS_ARCHITECTURE_UNKNOWN, "unknown" }
 };