drm/amdgpu/sdma: handle paging queues in amdgpu_sdma_reset_engine()

Need to properly start and stop paging queues if they are present.

This is not an issue today since we don't support a paging queue
on any chips with queue reset.

Fixes: b22659d5 ("drm/amdgpu: switch amdgpu_sdma_reset_engine to use the new sdma function pointers")
Reviewed-by: Jesse Zhang <Jesse.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>