Remove unused variable.

src/cache.c

@@ -1366,8 +1366,6 @@ struct keydata *keydata_alloc(char *data, size_t len)
 
 size_t keydata_walk(struct keydata **key, unsigned char **p, size_t cnt)
 {
-  size_t ret;
-
   if (*p == NULL)
     *p = (*key)->key;
   else if (*p == (*key)->key + KEYBLOCK_LEN)