crypto: arm64/gcm - Fix endianness warnings

This patch changes a couple u128's to be128 which is the correct
type to use and fixes a few sparse warnings.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>