drm/amdgpu: patch the IBs for the second UVD instance v2

Patch the IBs for the second UVD instance so that userspace don't need
to care about the instance they submit to.

v2: use direct IB patching

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-and-tested-by: James Zhu <James.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>