crypto: aes-gcm-p10 - Use the correct bit to test for P10

A hwcap feature bit is passed to cpu_has_feature, resulting in testing
for CPU_FTR_MMCRA instead of the 3.1 platform revision.

Fixes: c954b252 ("crypto: powerpc/p10-aes-gcm - Register modules as SIMD")
Reported-by: Nicolai Stange <nstange@suse.com>
Signed-off-by: Michal Suchanek <msuchanek@suse.de>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>