We can use devm to register keyboard backlight LED on hammer devices, this
will allow us to use HID's driver data for something else later.

Link: https://lore.kernel.org/r/20220228075446.466016-2-dmitry.torokhov@gmail.com
Tested-by: Stephen Boyd <swboyd@chromium.org> # coachz, wormdingler
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>