HID: i2c: use generic hidinput_input_event()

HID core provides the same functionality, so drop the custom handler.
Besides, the current handler doesn't schedule any outgoing report so it
did not work, anyway.

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>