drm/scheduler: move idle entities to scheduler with less load v2

This is the first attempt to move entities between schedulers to
have dynamic load balancing. We just move entities with no jobs for
now as moving the ones with jobs will lead to other compilcations
like ensuring that the other scheduler does not remove a job from
the current entity while we are moving.

v2: remove unused variable and an unecessary check

Signed-off-by: Nayan Deshmukh <nayan26deshmukh@gmail.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>