ARM: imx: include <asm/io.h> in hardware.h

As IOMEM is referenced in hardware.h, <asm/io.h> should be included
there.
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

arch/arm/mach-imx/hardware.h

@@ -20,6 +20,7 @@
 #ifndef __ASM_ARCH_MXC_HARDWARE_H__
 #define __ASM_ARCH_MXC_HARDWARE_H__
 
+#include <asm/io.h>
 #include <asm/sizes.h>
 
 #define addr_in_module(addr, mod) \