iommu-helper: unexport iommu_area_alloc

This function is only used by built-in code.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NAnshuman Khandual <khandual@linux.vnet.ibm.com>

lib/iommu-helper.c

@@ -3,7 +3,6 @@
  * IOMMU helper functions for the free area management
  */
 
-#include <linux/export.h>
 #include <linux/bitmap.h>
 #include <linux/bug.h>
 
@@ -38,4 +37,3 @@ unsigned long iommu_area_alloc(unsigned long *map, unsigned long size,
 	}
 	return -1;
 }
-EXPORT_SYMBOL(iommu_area_alloc);