HID: alps: allow incoming reports when only the trackstick is opened

If userspace only reads the trackstick node, and no one is listening to
the touchpad nor the hidraw node then, the device is not powered on.

Add open/close callbacks to allow users to disable the touchpad in Gnome
while keeping the trackstick active.

Link: https://bugzilla.redhat.com/show_bug.cgi?id=1559632
Link: https://gitlab.gnome.org/GNOME/mutter/issues/128


Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>