drm/amdgpu: switch default mes to uni mes

Switch the default mes to uni mes for gfx v12.
V2: remove uni_mes set for gfx v11.

Signed-off-by: Likun Gao <Likun.Gao@amd.com>
Reviewed-by: Jack Xiao <Jack.Xiao@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>