drm/amdgpu: add amdgpu_get_sdma_instance helper function
drm/amdgpu: add amdgpu_get_sdma_instance helper function

This function is added to map the ring to sdma instance

Signed-off-by: Jammy Zhou <302958b3037f7fa601b11152090f51ed851f29fd@amd.com>
Reviewed-by: Alex Deucher <08dc22c6156113f2deff178e35e3ed9b24d6af9e@amd.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs