nios2: move include asm-generic/io.h to end of file

Move asm-generic/io.h to end of file to override functions like
phys_to_virt, virt_to_phys in asm-generic/io.h.
This is due to recent commit 9216efaf introduced new way to
override functions by checking for the existence of a macro with the
same of the function.
Signed-off-by: NLey Foon Tan <lftan@altera.com>

arch/nios2/include/asm/io.h

@@ -24,8 +24,6 @@
 #define writew_relaxed(x, addr)	writew(x, addr)
 #define writel_relaxed(x, addr)	writel(x, addr)
 
-#include <asm-generic/io.h>
-
 extern void __iomem *__ioremap(unsigned long physaddr, unsigned long size,
 			unsigned long cacheflag);
 extern void __iounmap(void __iomem *addr);
@@ -57,4 +55,6 @@ static inline void iounmap(void __iomem *addr)
 #define virt_to_phys(vaddr)	\
 	((unsigned long)((unsigned long)(vaddr) & ~0xE0000000))
 
+#include <asm-generic/io.h>
+
 #endif /* _ASM_NIOS2_IO_H */