Input: maple_keyb - use guard notation when acquiring mutex

Using guard notation makes the code more compact and error handling
more robust by ensuring that mutexes are released in all code paths
when control leaves critical section.

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/keyboard/maple_keyb.c

···
 	 * We should always get the lock because the only
 	 * time it may be locked is if the driver is in the cleanup phase.
 	 */
-	if (likely(mutex_trylock(&maple_keyb_mutex))) {
-
+	scoped_guard(mutex_try, &maple_keyb_mutex) {
 		if (buf[1] == mapledev->function) {
 			memcpy(kbd->new, buf + 2, 8);
 			dc_scan_kbd(kbd);
 		}
-
-		mutex_unlock(&maple_keyb_mutex);
 	}
 }
 
···
 	struct maple_device *mdev = to_maple_dev(dev);
 	struct dc_kbd *kbd = maple_get_drvdata(mdev);
 
-	mutex_lock(&maple_keyb_mutex);
+	guard(mutex)(&maple_keyb_mutex);
 
 	input_unregister_device(kbd->dev);
 	kfree(kbd);
 
 	maple_set_drvdata(mdev, NULL);
-
-	mutex_unlock(&maple_keyb_mutex);
 	return 0;
 }