intel: Prepare registers so Windows drivers are happier

Change-Id: I12ebed30de4df9814ccb62341c7715fc62c7f5b9
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Signed-off-by: Pratik Prajapati <pratikkumar.v.prajapati@intel.com>
Reviewed-on: https://review.coreboot.org/23431
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/soc/intel/skylake/graphics.c

@@ -67,6 +67,8 @@ static void update_igd_opregion(igd_opregion_t *opregion)
 {
 	u16 reg16;
 
+	opregion->mailbox1.clid = 1;
+
 	/* Initialize Mailbox 3 */
 	opregion->mailbox3.bclp = IGD_BACKLIGHT_BRIGHTNESS;
 	opregion->mailbox3.pfit = IGD_FIELD_VALID | IGD_PFIT_STRETCH;