drm/i915/gvt: clean up the unused last_ctx_submit_time of struct intel_vgpu

Clean up it as it is not used now.
Signed-off-by: Changbin Du <changbin.du@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

drivers/gpu/drm/i915/gvt/gvt.h

@@ -165,7 +165,6 @@ struct intel_vgpu {
 	struct list_head workload_q_head[I915_NUM_ENGINES];
 	struct kmem_cache *workloads;
 	atomic_t running_workload_num;
-	ktime_t last_ctx_submit_time;
 	DECLARE_BITMAP(tlb_handle_pending, I915_NUM_ENGINES);
 	struct i915_gem_context *shadow_ctx;
 

drivers/gpu/drm/i915/gvt/handlers.c

@@ -1433,7 +1433,6 @@ static int elsp_mmio_write(struct intel_vgpu *vgpu, unsigned int offset,
 
 	execlist->elsp_dwords.data[execlist->elsp_dwords.index] = data;
 	if (execlist->elsp_dwords.index == 3) {
-		vgpu->last_ctx_submit_time = ktime_get();
 		ret = intel_vgpu_submit_execlist(vgpu, ring_id);
 		if(ret)
 			gvt_vgpu_err("fail submit workload on ring %d\n",