microblaze: Export memory_start for modules

memory_start symbol is needed by kernel modules.

Signed-off-by: Michal Simek <monstr@monstr.eu>
diff --git a/arch/microblaze/mm/init.c b/arch/microblaze/mm/init.c
index a44892e..a57cedf 100644
--- a/arch/microblaze/mm/init.c
+++ b/arch/microblaze/mm/init.c
@@ -41,6 +41,7 @@
  * have available.
  */
 unsigned long memory_start;
+EXPORT_SYMBOL(memory_start);
 unsigned long memory_end; /* due to mm/nommu.c */
 unsigned long memory_size;