drm/amdgpu: remove fulll access for suspend phase1

There is no need for gpu full access for suspend phase1
because under virtualization there is no hw register access
for dce block.

Signed-off-by: Yintian Tao <yttao@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>