drm/i915/gvt: emulate right behavior for tlb_control

Emulate right behavior for tlb_control, set to ZERO upon write.
Signed-off-by: NPing Gao <ping.a.gao@intel.com>
Signed-off-by: NMin He <min.he@intel.com>
Signed-off-by: NZhenyu Wang <zhenyuw@linux.intel.com>

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

@@ -1372,6 +1372,7 @@ static int gvt_reg_tlb_control_handler(struct intel_vgpu *vgpu,
 	unsigned int id = 0;
 
 	write_vreg(vgpu, offset, p_data, bytes);
+	vgpu_vreg(vgpu, offset) = 0;
 
 	switch (offset) {
 	case 0x4260: