drm/i915/gvt: Add GEN9_CLKGATE_DIS_4 to default BXT mmio handler

Host prints lots of untracked MMIO at 0x4653c when creating linux guest.
"gvt: vgpu 2: untracked MMIO 0004653c len 4"

GEN9_CLKGATE_DIS_4 (0x4653c) is accessed by i915 for gmbus clockgating.
However vgpu doesn't support any clockgating powergating operations
on related mmio access trap so need add it to default handler.
GEN9_CLKGATE_DIS_4 is accessed in bxt_gmbus_clock_gating() which only
applies to GEN9_LP so doens't show the warning on other platforms.

The solution is to add it to default handler init_bxt_mmio_info().
Reviewed-by: NHe, Min <min.he@intel.com>
Signed-off-by: NColin Xu <colin.xu@intel.com>
Signed-off-by: NZhenyu Wang <zhenyuw@linux.intel.com>

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

@@ -3210,6 +3210,7 @@ static int init_bxt_mmio_info(struct intel_gvt *gvt)
 	MMIO_D(BXT_DSI_PLL_ENABLE, D_BXT);
 
 	MMIO_D(GEN9_CLKGATE_DIS_0, D_BXT);
+	MMIO_D(GEN9_CLKGATE_DIS_4, D_BXT);
 
 	MMIO_D(HSW_TVIDEO_DIP_GCP(TRANSCODER_A), D_BXT);
 	MMIO_D(HSW_TVIDEO_DIP_GCP(TRANSCODER_B), D_BXT);