[ARM] Orion: fix for tsx09-common.c compilation problem

In some cases, compilation of the tsx09 common file was failing due
to an incomplete list of includes.
Signed-off-by: Sylver Bruneau <sylver.bruneau@googlemail.com>
Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>

arch/arm/mach-orion5x/tsx09-common.c

@@ -13,6 +13,7 @@
 #include <linux/kernel.h>
 #include <linux/pci.h>
 #include <linux/mv643xx_eth.h>
+#include <linux/timex.h>
 #include <linux/serial_reg.h>
 #include "tsx09-common.h"