[MIPS] Export empty_zero_page for sake of the ext4 module.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/mm/init.c b/arch/mips/mm/init.c
index ecd562d..137c14b 100644
--- a/arch/mips/mm/init.c
+++ b/arch/mips/mm/init.c
@@ -71,6 +71,7 @@
  * don't have to care about aliases on other CPUs.
  */
 unsigned long empty_zero_page, zero_page_mask;
+EXPORT_SYMBOL_GPL(empty_zero_page);
 
 /*
  * Not static inline because used by IP27 special magic initialization code