add missing __iomem to generic iounmap declaration

Signed-off-by: Mark Salter <[e-mail]>
Acked-by: Arnd Bergmann <[e-mail]>

include/asm-generic/io.h

···
 #define ioremap_wc ioremap_nocache
 #endif
 
-static inline void iounmap(void *addr)
+static inline void iounmap(void __iomem *addr)
 {
 }
 #endif /* CONFIG_MMU */