drm/amdgpu: add mes unmap legacy queue routine

For mes kiq has been taken over by mes sched, drv can't directly
use mes kiq to unmap queues. drv has to use mes sched api to
unmap legacy queue.

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>