drm/amdgpu/powerplay: enable LEDs on Fiji boards

This enables the LEDs that light up based on DPM states
on some Fiji boards.

bug:
https://bugs.freedesktop.org/show_bug.cgi?id=97590



Reviewed-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>