arm: Export empty_zero_page for ZERO_PAGE usage in modules.

ext4 uses ZERO_PAGE(0) to zero out blocks.  We need to export
different symbols in different arches for the usage of ZERO_PAGE
in modules.
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

arch/arm/mm/mmu.c

@@ -35,6 +35,7 @@ extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
  * zero-initialized data and COW.
  */
 struct page *empty_zero_page;
+EXPORT_SYMBOL(empty_zero_page);
 
 /*
  * The pmd table for the upper-most set of pages.