crypto: arch - use crypto_memneq instead of memcmp

Replace remaining occurences (just as we did in crypto/) under arch/*/crypto/
that make use of memcmp() for comparing keys or authentication tags for
usage with crypto_memneq(). It can simply be used as a drop-in replacement
for the normal memcmp().

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Cc: James Yonan <james@openvpn.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>