drm/amdgpu: fix compute queue priority if num_kcq is less than 4

Compute queues are configurable with module param, num_kcq.
amdgpu_gfx_is_high_priority_compute_queue was setting 1st 4 queues to
high priority queue leaving a null drm scheduler in
adev->gpu_sched[hw_ip]["normal_prio"].sched if num_kcq < 5.

This patch tries to fix it by alternating compute queue priority between
normal and high priority.

Fixes: 33abcb1f

 (drm/amdgpu: set compute queue priority at mqd_init)
Signed-off-by: Nirmoy Das <nirmoy.das@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>