drm/scheduler: improve job distribution with multiple queues

drm/scheduler: improve job distribution with multiple queues

This patch uses score to select a new drm scheduler for better
loadbalance between multiple drm schedulers instead of num_jobs.

Below are test results after running amdgpu_test for ~10 times.

Before this patch:

sched_name     num of many times it got schedule
=========      ==================================
sdma0          1463
sdma1          198
comp_1.0.1     280

After this patch:

sched_name     num of many times it got schedule
=========      ==================================
sdma0          925
sdma1          928
comp_1.0.1     177
comp_1.1.1     44
comp_1.2.1     43
comp_1.3.1     44

Signed-off-by: Nirmoy Das <nirmoy.das@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/373000/
Signed-off-by: Christian König <christian.koenig@amd.com>