KEYS: potential uninitialized variable

If __key_link_begin() failed then "edit" would be uninitialized.  I've
added a check to fix that.

Change-Id: I0e28bdba07f645437db2b08daf67ca27f16c6f5c
Fixes: f70e2e0 ('KEYS: Do preallocation for __key_link()')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

security/keys/key.c

@@ -580,7 +580,7 @@ int key_reject_and_link(struct key *key,
 
 	mutex_unlock(&key_construction_mutex);
 
-	if (keyring)
+	if (keyring && link_ret == 0)
 		__key_link_end(keyring, key->type, prealloc);
 
 	/* wake up anyone waiting for a key to be constructed */