keys: Add a 'recurse' flag for keyring searches

Add a 'recurse' flag for keyring searches so that the flag can be omitted
and recursion disabled, thereby allowing just the nominated keyring to be
searched and none of the children.

Signed-off-by: David Howells <dhowells@redhat.com>
diff --git a/include/linux/key.h b/include/linux/key.h
index fb2debc..ff10273 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -341,7 +341,8 @@ extern int keyring_clear(struct key *keyring);
 
 extern key_ref_t keyring_search(key_ref_t keyring,
 				struct key_type *type,
-				const char *description);
+				const char *description,
+				bool recurse);
 
 extern int keyring_add_key(struct key *keyring,
 			   struct key *key);