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>
diff --git a/arch/arm/mach-imx/hardware.h b/arch/arm/mach-imx/hardware.h
index 356131f..a3b0b04 100644
--- a/arch/arm/mach-imx/hardware.h
+++ b/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) \