crypto: arm/ghash-ce - enable module autoloading based on CPU feature bits

Make the module autoloadable by tying it to the CPU feature bit that
describes whether the optional instructions it relies on are implemented
by the current CPU.

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