X.509: Make algo identifiers text instead of enum

Make the identifier public key and digest algorithm fields text instead of
enum.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>

kernel/module_signing.c

@@ -16,6 +16,12 @@
 #include <crypto/public_key.h>
 #include "module-internal.h"
 
+enum pkey_id_type {
+	PKEY_ID_PGP,		/* OpenPGP generated key ID */
+	PKEY_ID_X509,		/* X.509 arbitrary subjectKeyIdentifier */
+	PKEY_ID_PKCS7,		/* Signature in PKCS#7 message */
+};
+
 /*
  * Module signature information block.
  *