drm/amdgpu: enable SDMA usermode queues

drm/amdgpu: enable SDMA usermode queues

This patch does necessary modifications to enable the SDMA
usermode queues using the existing userqueue infrastructure.

V9:  introduced this patch in the series
V10: use header file instead of extern (Alex)
V11: rename drm_amdgpu_userq_mqd_sdma_gfx_v11 to
     drm_amdgpu_userq_mqd_sdma_gfx11 (Marek)

Cc: Christian König <Christian.Koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Shashank Sharma <shashank.sharma@amd.com>
Signed-off-by: Arvind Yadav <arvind.yadav@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>