drm/amdgpu/gfx: enable mes to map legacy queue support

Enable mes to map legacy queue support.

v2: drop unused gfx_v12_0_kiq_enable_kgq() (Alex)

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