[ARM] iop13xx: avoid polluting the kernel's namespace

Avoid unnecessarily pollution of the kernel's namespace by avoiding
mach/hardware.h in mach/timex.h.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mach-iop13xx/include/mach/timex.h

-#include <mach/hardware.h>
-
 #define CLOCK_TICK_RATE (100 * HZ)