Input: bcm5974 - set BUTTONPAD property

Some bcm5974 trackpads have a physical button beneath the physical surface.
This patch sets the property bit so user space applications can detect the
trackpad type and act accordingly.

Signed-off-by: Jussi Pakkanen <[e-mail]>
Reviewed-by: Henrik Rydberg <[e-mail]>
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/mouse/bcm5974.c

···
 	__set_bit(BTN_TOOL_QUADTAP, input_dev->keybit);
 	__set_bit(BTN_LEFT, input_dev->keybit);
 
+	if (cfg->caps & HAS_INTEGRATED_BUTTON)
+		__set_bit(INPUT_PROP_BUTTONPAD, input_dev->propbit);
+
 	input_set_events_per_packet(input_dev, 60);
 }