nb/intel/x4x/x4x.h: Include iomap.h

This is needed for the definition of the MCHBARx() macros.

Change-Id: I654344451c0568f306f39365fd07371b2d6cff04
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/36555
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/northbridge/intel/x4x/x4x.h

@@ -18,6 +18,8 @@
 #ifndef __NORTHBRIDGE_INTEL_X4X_H__
 #define __NORTHBRIDGE_INTEL_X4X_H__
 
+#include "iomap.h"
+
 /*
  * D0:F0
  */