drm/i915/gvt: Remove one duplicated MMIO

Remove one duplicated MMIO GEN6_PCODE_MAILBOX. Duplicated MMIO will
cause host GVT-g initialization failure.

Fixes: 9c3a16c887f0 ("drm/i915/hsw+: Add support for multiple power well regs")
Signed-off-by: Jian Jun Chen <jian.jun.chen@intel.com>
Acked-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

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

@@ -2659,7 +2659,6 @@ static int init_skl_mmio_info(struct intel_gvt *gvt)
 	MMIO_D(HSW_PWR_WELL_CTL_BIOS(SKL_DISP_PW_MISC_IO), D_SKL_PLUS);
 	MMIO_DH(HSW_PWR_WELL_CTL_DRIVER(SKL_DISP_PW_MISC_IO), D_SKL_PLUS, NULL,
 		skl_power_well_ctl_write);
-	MMIO_DH(GEN6_PCODE_MAILBOX, D_SKL_PLUS, NULL, mailbox_write);
 
 	MMIO_D(0xa210, D_SKL_PLUS);
 	MMIO_D(GEN9_MEDIA_PG_IDLE_HYSTERESIS, D_SKL_PLUS);