Input: hp680_ts_input - ensure arguments to request_irq and free_irq are compatible

Change 0 to NULL in the last argument of request_irq, since the argument
should have pointer type and so that the last argument of request_irq
syntactically matches the second argument of the later call to free_irq.

Signed-off-by: Julia Lawall <[e-mail]>
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/touchscreen/hp680_ts_input.c

···
 	hp680_ts_dev->phys = "hp680_ts/input0";
 
 	if (request_irq(HP680_TS_IRQ, hp680_ts_interrupt,
-			0, MODNAME, 0) < 0) {
+			0, MODNAME, NULL) < 0) {
 		printk(KERN_ERR "hp680_touchscreen.c: Can't allocate irq %d\n",
 		       HP680_TS_IRQ);
 		err = -EBUSY;