treewide: Add 'IWYU pragma: export' comment

This pragma says to IWYU (Include What You Use) that the current file
is supposed to provide commented headers.

Change-Id: I482c645f6b5f955e532ad94def1b2f74f15ca908
Signed-off-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/68332
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>
diff --git a/src/southbridge/intel/lynxpoint/pch.h b/src/southbridge/intel/lynxpoint/pch.h
index 7d9fc6d..1623274 100644
--- a/src/southbridge/intel/lynxpoint/pch.h
+++ b/src/southbridge/intel/lynxpoint/pch.h
@@ -4,6 +4,7 @@
 #define SOUTHBRIDGE_INTEL_LYNXPOINT_PCH_H
 
 #include <acpi/acpi.h>
+#include <southbridge/intel/common/rcba.h> /* IWYU pragma: export */
 
 #define CROS_GPIO_DEVICE_NAME	"LynxPoint"
 
@@ -55,8 +56,6 @@
 #define DEFAULT_GPIOSIZE	0x80
 #endif
 
-#include <southbridge/intel/common/rcba.h>
-
 #ifndef __ACPI__
 
 #if CONFIG(INTEL_LYNXPOINT_LP)