crypto: ghash-clmulni - Fix load failure

ghash_clmulni_intel fails to load on Linux 4.3+ with the following message:
"modprobe: ERROR: could not insert 'ghash_clmulni_intel': Invalid argument"

After 8996eafd

 ("crypto: ahash - ensure statesize is non-zero") all ahash
drivers are required to implement import()/export(), and must have a non-
zero statesize.

This patch has been tested with the algif_hash interface. The calculated
digest values, after several rounds of import()s and export()s, match those
calculated by tcrypt.

Signed-off-by: Rui Wang <rui.y.wang@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>