ARC: Add read*_relaxed to asm/io.h

Some drivers require these, and ARC didn't had them yet.
Signed-off-by: Mischa Jonker <mjonker@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/include/asm/io.h

@@ -100,6 +100,10 @@ static inline void __raw_writel(u32 w, volatile void __iomem *addr)
 
 }
 
+#define readb_relaxed readb
+#define readw_relaxed readw
+#define readl_relaxed readl
+
 #include <asm-generic/io.h>
 
 #endif /* _ASM_ARC_IO_H */