nios2: include linux/type.h in io.h

This is require for __iomem definition.
Signed-off-by: Ley Foon Tan <lftan@altera.com>

arch/nios2/include/asm/io.h

@@ -11,6 +11,7 @@
 #ifndef _ASM_NIOS2_IO_H
 #define _ASM_NIOS2_IO_H
 
+#include <linux/types.h>
 #include <asm/pgtable-bits.h>
 
 /* PCI is not supported in nios2, set this to 0. */