HID: asus: drop dependency on I2C_HID

There is nothing transport-specific in this driver, and we will now be
adding support for some Asus USB devices too.

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