crypto: arm64/gcm-aes-ce - remove non-SIMD fallback path

Now that kernel mode SIMD is guaranteed to be available when executing
in task or softirq context, we no longer need scalar fallbacks to use
when the NEON is unavailable. So get rid of them.

Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>