KEYS: Store public key algo ID in public_key_signature struct

Store public key algorithm ID in public_key_signature struct for reference
purposes.  This allows a public_key_signature struct to be embedded in
struct x509_certificate and other places more easily.
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Reviewed-by: NKees Cook <keescook@chromium.org>
Reviewed-by: NJosh Boyer <jwboyer@redhat.com>

include/crypto/public_key.h

@@ -90,6 +90,7 @@ struct public_key_signature {
 	u8 *digest;
 	u8 digest_size;			/* Number of bytes in digest */
 	u8 nr_mpi;			/* Occupancy of mpi[] */
+	enum pkey_algo pkey_algo : 8;
 	enum pkey_hash_algo pkey_hash_algo : 8;
 	union {
 		MPI mpi[2];