drm/amdgpu: Avoid accessing HW when suspending SW state

At this point the ASIC is already post reset by the HW/PSP
so the HW not in proper state to be configured for suspension,
some blocks might be even gated and so best is to avoid touching it.

v2: Rename in_dpc to more meaningful name

Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>