crypto: aes-generic - drop alignment requirement

The generic AES code exposes a 32-bit align mask, which forces all
users of the code to use temporary buffers or take other measures to
ensure the alignment requirement is adhered to, even on architectures
that don't care about alignment for software algorithms such as this
one.

So drop the align mask, and fix the code to use get_unaligned_le32()
where appropriate, which will resolve to whatever is optimal for the
architecture.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>