evdev: Only init a pointer if the evdev device has a button

We used to test for abs | rel | button,  which inits a pointer device for
a device with just rel or abs capabilities.  We now make sure we have either
rel or abs as well as button.

src/evdev.c

@@ -555,8 +555,8 @@ evdev_handle_device(struct evdev_device *device)
 static int
 evdev_configure_device(struct evdev_device *device)
 {
-	if ((device->caps &
-	     (EVDEV_MOTION_ABS | EVDEV_MOTION_REL | EVDEV_BUTTON))) {
+	if ((device->caps & (EVDEV_MOTION_ABS | EVDEV_MOTION_REL)) &&
+	    (device->caps & EVDEV_BUTTON)) {
 		weston_seat_init_pointer(device->seat);
 		weston_log("input device %s, %s is a pointer caps =%s%s%s\n",
 			   device->devname, device->devnode,