crypto: arm/ghash - change internal cra_name to "__ghash"

The fact that the internal synchrous hash implementation is called
"ghash" like the publicly visible one is causing the testmgr code
to misidentify it as an algorithm that requires testing at boottime.
So rename it to "__ghash" to prevent this.

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