crypto: arm/ghash - provide a synchronous version

GHASH is used by the GCM mode, which is often used in contexts where
only synchronous ciphers are permitted. So provide a synchronous version
of GHASH based on the existing code. This requires a non-SIMD fallback
to deal with invocations occurring from a context where SIMD instructions
may not be used.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>