Input: fix polling of /proc/bus/input/devices

Tested-by: NAlessio Sangalli <alesan@manoweb.com>
Signed-off-by: NDmitry Torokhov <dtor@mail.ru>

drivers/input/input.c

@@ -744,11 +744,11 @@ static inline void input_wakeup_procfs_readers(void)
 
 static unsigned int input_proc_devices_poll(struct file *file, poll_table *wait)
 {
-	int state = input_devices_state;
-
 	poll_wait(file, &input_devices_poll_wait, wait);
-	if (state != input_devices_state)
+	if (file->f_version != input_devices_state) {
+		file->f_version = input_devices_state;
 		return POLLIN | POLLRDNORM;
+	}
 
 	return 0;
 }