nb/intel/gm45/igd: Hide IGD while disabling

Hide the IGD to make sure ramstage doesn't detect it.

Change-Id: If389016f3bb0c4c2fd0b826914997a87a9137201
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/18194
Tested-by: build bot (Jenkins)
Reviewed-by: Nico Huber <nico.h@gmx.de>
diff --git a/src/northbridge/intel/gm45/igd.c b/src/northbridge/intel/gm45/igd.c
index 74572ca..1164339 100644
--- a/src/northbridge/intel/gm45/igd.c
+++ b/src/northbridge/intel/gm45/igd.c
@@ -127,6 +127,11 @@
 		MCHBAR16(0x119e) = (MCHBAR16(0x119e) & ~(7 << 13)) | (4 << 13);
 		MCHBAR16(0x119e) |= (1 << 12);
 	}
+
+	/* Hide IGD. */
+	u32 deven = pci_read_config32(mch_dev, D0F0_DEVEN);
+	deven &= ~(3 << 3);
+	pci_write_config32(mch_dev, D0F0_DEVEN, deven);
 }
 
 void init_igd(const sysinfo_t *const sysinfo)