BACKPORT/FROMGIT: drm/amd/amdgpu: Enabling Power Gating for Stoney platform

Removed condition checks to skip the power gating feature for
stoney platform.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Vijendar Mukunda <vijendar.mukunda@amd.com>
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

(cherry picked from commit 1062ddb6
git://anongit.freedesktop.org/drm/drm of origin/drm-next branch)

Conflicts:
       drivers/gpu/drm/amd/amdgpu/amdgpu_acp.c
       [Hang Zhou] Fixed trivial rebase conflicts due to skepping patches.

BUG=b:117711307
TEST=Build & Boot on Careen

Change-Id: I3f429a1bcf4d9334e305f4248c79bb2c2464f29c
Reviewed-on: https://chromium-review.googlesource.com/1294553


Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Hang Zhou <hang.zhou@amd.corp-partner.google.com>
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>