crypto: api - Add CRYPTO_MINALIGN_ATTR to struct crypto_alg

The struct crypto_alg is embedded into various type-specific structs
such as aead_alg.  This is then used as part of instances such as
struct aead_instance.  It is also embedded into the generic struct
crypto_instance.  In order to ensure that struct aead_instance can
be converted to struct crypto_instance when necessary, we need to
ensure that crypto_alg is aligned properly.

This patch adds an alignment attribute to struct crypto_alg to
ensure this.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>