Input: ff-core - silence an underflow warning

My static checker complains that "value" comes from the user in
evdev_do_ioctl() and we check that it's not too large here but we don't
check that it's negative.  It's harmless because the ->set_gain() and
->set_autocenter() functions truncate it to a valid u16 value, but we
may as well fix it just to make the static checker happy.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/ff-core.c

@@ -273,14 +273,14 @@ int input_ff_event(struct input_dev *dev, unsigned int type,
 
 	switch (code) {
 	case FF_GAIN:
-		if (!test_bit(FF_GAIN, dev->ffbit) || value > 0xffff)
+		if (!test_bit(FF_GAIN, dev->ffbit) || value > 0xffffU)
 			break;
 
 		ff->set_gain(dev, value);
 		break;
 
 	case FF_AUTOCENTER:
-		if (!test_bit(FF_AUTOCENTER, dev->ffbit) || value > 0xffff)
+		if (!test_bit(FF_AUTOCENTER, dev->ffbit) || value > 0xffffU)
 			break;
 
 		ff->set_autocenter(dev, value);