cbfstool: add aarch64 as a name

The aarch64 is not really an arm variant, it's sufficiently
different that it can be considered (for purposes of cbfs, certainly)
to be a new architecture.

Add a constant in cbfs.h and strings to correspond to it.
Note that with the new cbfstool support that we added earlier,
the actual use of aarch64 ELF files actually "just works" (at
least when tested earlier).

Change-Id: Ib4900900d99c9aae6eef858d8ee097709368c4d4
Reviewed-on: https://chromium-review.googlesource.com/180221
Reviewed-by: Stefan Reinauer <reinauer@chromium.org>
Commit-Queue: Ronald Minnich <rminnich@chromium.org>
Tested-by: Ronald Minnich <rminnich@chromium.org>
(cherry picked from commit f836e14695827b2667804bc1058e08ec7b297921)
Signed-off-by: Isaac Christensen <isaac.christensen@se-eng.com>
Reviewed-on: http://review.coreboot.org/6896
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

util/cbfstool/common.c

@@ -130,6 +130,7 @@ static struct {
 	uint32_t arch;
 	const char *name;
 } arch_names[] = {
+	{ CBFS_ARCHITECTURE_AARCH64, "aarch64" },
 	{ CBFS_ARCHITECTURE_ARM, "arm" },
 	{ CBFS_ARCHITECTURE_X86, "x86" },
 	{ CBFS_ARCHITECTURE_UNKNOWN, "unknown" }