drm/amdgpu: remove non gfx specific handling from sdma_v4_0_gfx_resume

Needed to start using the paging queue.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>