drm/i915/gvt: Init vreg GUC_STATUS to GS_MIA_IN_RESET

Although GVT doesn't support guest GuC, MIA core is still expected
to be GS_MIA_IN_RESET after uc HW reset.

Reviewed-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Colin Xu <colin.xu@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20200819010900.54598-1-colin.xu@intel.com