HID: add inliners for ll_driver transport-layer callbacks

Those callbacks are not mandatory, so it's better to add inliners
to use them safely.

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