amdgpu: add amdgpu_cs_submit_gang api
The amdgpu_cs_submit_gang api can be used to submit ibs from different HW IP as single entity.
Signed-off-by: Yogesh Mohan Marimuthu yogesh.mohanmarimuthu@amd.com Reviewed-by: Vitaly Prosyak vitaly.prosyak@amd.com