drm/amdgpu: remove fence_lock

Was never used as far as I can see.

Signed-off-by: Christian König <[e-mail]>
Reviewed-by: Chunming Zhou <[e-mail]>
Reviewed-by: Edward O'Callaghan <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

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

···
 	struct amdgpu_fence_driver	fence_drv;
 	struct amd_gpu_scheduler	sched;
 
-	spinlock_t              fence_lock;
 	struct amdgpu_bo	*ring_obj;
 	volatile uint32_t	*ring;
 	unsigned		rptr_offs;

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

···
 	ring->cond_exe_gpu_addr = adev->wb.gpu_addr + (ring->cond_exe_offs * 4);
 	ring->cond_exe_cpu_addr = &adev->wb.wb[ring->cond_exe_offs];
 
-	spin_lock_init(&ring->fence_lock);
 	r = amdgpu_fence_driver_start_ring(ring, irq_src, irq_type);
 	if (r) {
 		dev_err(adev->dev, "failed initializing fences (%d).\n", r);