crypto: cmac - fix alignment of 'consts'

The per-transform 'consts' array is accessed as __be64 in
crypto_cmac_digest_setkey() but was only guaranteed to be aligned to
__alignof__(long).  Fix this by aligning it to __alignof__(__be64).

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>