drm/amdgpu: Initialize and update SDMA power gating

Init SDMA HW base configuration and enable idle INT for rn.

Signed-off-by: Prike Liang <Prike.Liang@amd.com>
Reviewed-by: Aaron Liu <aaron.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>