iommu-helper: unexport iommu_area_alloc

This function is only used by built-in code.

Signed-off-by: Christoph Hellwig <[e-mail]>
Reviewed-by: Anshuman Khandual <[e-mail]>

lib/iommu-helper.c

···
  * IOMMU helper functions for the free area management
  */
 
-#include <linux/export.h>
 #include <linux/bitmap.h>
 #include <linux/bug.h>
 
···
 	}
 	return -1;
 }
-EXPORT_SYMBOL(iommu_area_alloc);