ns: rename to __ns_ref

Make it easier to grep and rename to ns_count.

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

kernel/pid.c

@@ -71,7 +71,7 @@ static int pid_max_max = PID_MAX_LIMIT;
  * the scheme scales to up to 4 million PIDs, runtime.
  */
 struct pid_namespace init_pid_ns = {
-	.ns.count = REFCOUNT_INIT(2),
+	.ns.__ns_ref = REFCOUNT_INIT(2),
 	.idr = IDR_INIT(init_pid_ns.idr),
 	.pid_allocated = PIDNS_ADDING,
 	.level = 0,