drm/amdgpu: drop runtime pm disablement quirk on several sienna cichlid cards

This quirk is not needed any more as it's fixed by bypassing
SMU FW reloading in runtime resume.

Signed-off-by: Guchun Chen <guchun.chen@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>