drm/amdgpu: set compute queue priority at mqd_init

We were changing compute ring priority while rings were being used
before every job submission which is not recommended. This patch
sets compute queue priority at mqd initialization for gfx8, gfx9 and
gfx10.

Policy: make queue 0 of each pipe as high priority compute queue

High/normal priority compute sched lists are generated from set of high/normal
priority compute queues. At context creation, entity of compute queue
get a sched list from high or normal priority depending on ctx->priority

Signed-off-by: Nirmoy Das <nirmoy.das@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>