arm: Add export.h to ARM specific files as required.

These files all make use of one of the EXPORT_SYMBOL variants
or the THIS_MODULE macro.  So they will need <linux/export.h>

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index 04e9a92..fbdd12e 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -13,6 +13,7 @@
 #include <linux/init.h>
 #include <linux/bootmem.h>
 #include <linux/mman.h>
+#include <linux/export.h>
 #include <linux/nodemask.h>
 #include <linux/initrd.h>
 #include <linux/of_fdt.h>