drm/amd/pm: do not use ixFEATURE_STATUS for checking smc running

This reverts commit f8781228 ("drm/amdgpu:
Fix bug where DPM is not enabled after hibernate and resume").
It was intended to fix Hawaii S4(hibernation) issue but break S3. As
ixFEATURE_STATUS is filled with garbage data on resume which can be
only cleared by reloading smc firmware(but that will involve many
changes). So, we will revert this S4 fix and seek a new way.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Tested-by: Sandeep Raghuraman <sandy.8925@gmail.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>