mx5: Fix build error for mx51_defconfig

Need to include <asm/div64.h> for do_div calls.
Signed-off-by: Dinh Nguyen <Dinh.Nguyen@freescale.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

arch/arm/mach-mx5/clock-mx51.c

@@ -16,6 +16,7 @@
 #include <linux/io.h>
 
 #include <asm/clkdev.h>
+#include <asm/div64.h>
 
 #include <mach/hardware.h>
 #include <mach/common.h>