HID: waltop: Remove waltop_probe() and waltop_remove() functions

The waltop_probe() and waltop_remove() functions do not have any special
initialization and cleanup. Remove them and let HID core handle the default
probe/remove actions.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Nikolai Kondrashov <spbnick@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>