KEYS: Store public key algo ID in public_key struct

Store public key algo ID in public_key struct for reference purposes.  This
allows it to be removed from the x509_certificate struct and used to find a
default in public_key_verify_signature().

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Josh Boyer <jwboyer@redhat.com>

include/crypto/public_key.h

@@ -60,6 +60,7 @@ struct public_key {
 #define PKEY_CAN_DECRYPT	0x02
 #define PKEY_CAN_SIGN		0x04
 #define PKEY_CAN_VERIFY		0x08
+	enum pkey_algo pkey_algo : 8;
 	enum pkey_id_type id_type : 8;
 	union {
 		MPI	mpi[5];