MIPS: SEAD3: Collect LED platform device registration in a single file.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Cc: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Bryan Wu <cooloney@gmail.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: linux-leds@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/8203/