southbridge/intel/fsp_rangeley: fix to include irqroute.h twice

This matches what was done on baytrail in commit bfca984b -
soc/intel/fsp_baytrail: set up for including irqroute.h twice

irq_helper.h intentionally gets included into irqroute.asl twice - once
for pic mode and once for apic mode.  Since people are used to seeing
guard statements on the .h files, add the guards to irqroute.h and add
a comment to irq_helper.h explaining why they aren't there.

Change-Id: I709f9370ce7db1b3ffac2297aeaba5cc670ec20c
Signed-off-by: Martin Roth <martin.roth@se-eng.com>
Reviewed-on: http://review.coreboot.org/6606
Tested-by: build bot (Jenkins)
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>

src/mainboard/intel/mohonpeak/irqroute.h

@@ -18,6 +18,9 @@
  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+#ifndef IRQROUTE_H
+#define IRQROUTE_H
+
 #include <southbridge/intel/fsp_rangeley/irq.h>
 #include <southbridge/intel/fsp_rangeley/pci_devs.h>
 
@@ -66,3 +69,5 @@
 	PIRQ_PIC(F, 15), \
 	PIRQ_PIC(G, 14), \
 	PIRQ_PIC(H, 15)
+
+#endif /* IRQROUTE_H */

src/southbridge/intel/fsp_rangeley/acpi/irq_helper.h

@@ -18,6 +18,11 @@
  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+/*
+ * This file intentionally gets included multiple times, to set pic and apic
+ * modes, so should not have guard statements added.
+ */
+
 /*
  * This file will use irqroute.asl and mainboard/irqroute.h
  * to generate the ACPI IRQ routing for the mainboard being compiled.
@@ -29,6 +34,7 @@
 #undef PCI_DEV_PIRQ_ROUTE
 #undef PIRQ_PIC_ROUTES
 #undef PIRQ_PIC
+#undef IRQROUTE_H
 
 #if defined(PIC_MODE)