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/include/device/pci_ops.h b/src/include/device/pci_ops.h
index a167825..b5d4e23 100644
--- a/src/include/device/pci_ops.h
+++ b/src/include/device/pci_ops.h
@@ -6,7 +6,7 @@
 #include <stdint.h>
 #include <device/device.h>
 #include <device/pci_type.h>
-#include <arch/pci_ops.h>
+#include <arch/pci_ops.h> /* IWYU pragma: export */
 
 void __noreturn pcidev_die(void);