drm/amdgpu: disable some gfx light sleep

temporarily disable to avoid s3 test failure.

s3 test failure log:
"[drm:amdgpu_job_timedout [amdgpu]] *ERROR* ring sdma0 timeout,
signaled seq=8278, emitted seq=8281"

Reviewed-by: Jack Xiao <Jack.Xiao@amd.com>
Signed-off-by: Tianci Yin <tianci.yin@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>