drm/amdgpu: abstract amdgpu_job for scheduler

drivers/gpu/drm/amd/amdgpu/amdgpu.h

drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c

drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c

drivers/gpu/drm/amd/amdgpu/amdgpu_sched.c

drivers/gpu/drm/amd/amdgpu/amdgpu_uvd.c

drivers/gpu/drm/amd/amdgpu/amdgpu_vce.c

drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c

drivers/gpu/drm/amd/scheduler/gpu_scheduler.c

drivers/gpu/drm/amd/scheduler/gpu_scheduler.h