Fix build: only set iommu buswide flag if IOMMU code is included.

Sponsored by:	Innovate DSbD

sys/dev/ahci/ahci_pci.c

@@ -27,6 +27,8 @@
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include "opt_iommu.h"
+
 #include <sys/param.h>
 #include <sys/module.h>
 #include <sys/systm.h>
@@ -499,6 +501,7 @@ ahci_pci_attach(device_t dev)
 		i++;
 	ctlr->quirks = ahci_ids[i].quirks;
 
+#ifdef IOMMU
 	if (ctlr->quirks & AHCI_Q_IOMMU_BUSWIDE) {
 		/*
 		 * The controller issues DMA requests from PCI function 1,
@@ -507,6 +510,7 @@ ahci_pci_attach(device_t dev)
 		 */
 		bus_dma_iommu_set_buswide(dev);
 	}
+#endif
 
 	/* Limit speed for my onboard JMicron external port.
 	 * It is not eSATA really, limit to SATA 1 */