drm/amdgpu/sdma5.2: implement ring reset callback for sdma5.2

Implement sdma queue reset callback via MMIO.

v2: enter/exit safemode for mmio queue reset.

Signed-off-by: Jiadong Zhu <Jiadong.Zhu@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>