iommu/amd: Add include of <linux/irqreturn.h>

We currently include <linux/irqreturn.h> in <linux/pci.h>, but I'm about to
remove that from linux/pci.h, so add explicit includes where needed.
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

drivers/iommu/amd_iommu_types.h

@@ -25,6 +25,7 @@
 #include <linux/list.h>
 #include <linux/spinlock.h>
 #include <linux/pci.h>
+#include <linux/irqreturn.h>
 
 /*
  * Maximum number of IOMMUs supported