platform/surface: surfacepro3_button: Drop wakeup source on remove

platform/surface: surfacepro3_button: Drop wakeup source on remove

The wakeup source added by device_init_wakeup() in surface_button_add()
needs to be dropped during driver removal, so update the driver to do
that.

Fixes: 19351f340765 ("platform/x86: surfacepro3: Support for wakeup from suspend-to-idle")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://patch.msgid.link/4368848.1IzOArtZ34@rafael.j.wysocki
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>