arm: Only support ARM64_CRC32 when using GCC

Today, only gcc has __builtin_aarch64_crc32b (clang-16 does not, for
example). Make this option depend on CC_IS_GCC.

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
1 file changed