Revert "drm/amdgpu: Fix NULL dereference in dpm sysfs handlers"

commit 87004abf upstream.

This regressed some working configurations so revert it.  Will
fix this properly for 5.9 and backport then.

This reverts commit 38e0c89a

.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>