crypto: cbcmac - remove unnecessary alignment logic

The cbcmac template is aligning a field in its desc context to the
alignmask of its underlying 'cipher', at runtime.  This is almost
entirely pointless, since cbcmac is already using the cipher API
functions that handle alignment themselves, and few ciphers set a
nonzero alignmask anyway.  Also, even without runtime alignment, an
alignment of at least 4 bytes can be guaranteed.

Thus, at best this code is optimizing for the rare case of ciphers that
set an alignmask >= 7, at the cost of hurting the common cases.

Therefore, remove the manual alignment code from cbcmac.

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