alpha: Add export.h for THIS_MODULE/EXPORT_SYMBOL

These files were getting it via the implicit module.h
presence that was everywhere.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/arch/alpha/kernel/pci_iommu.c b/arch/alpha/kernel/pci_iommu.c
index 022c2748..4361080 100644
--- a/arch/alpha/kernel/pci_iommu.c
+++ b/arch/alpha/kernel/pci_iommu.c
@@ -7,6 +7,7 @@
 #include <linux/pci.h>
 #include <linux/gfp.h>
 #include <linux/bootmem.h>
+#include <linux/export.h>
 #include <linux/scatterlist.h>
 #include <linux/log2.h>
 #include <linux/dma-mapping.h>