mn10300: io: implement dummy relaxed accessor macros for writes

write{b,w,l}_relaxed are implemented by some architectures in order to
permit memory-mapped I/O accesses with weaker barrier semantics than the
non-relaxed variants.

This patch adds dummy macros for the write accessors to mn10300, in the
same vein as the dummy definitions for the relaxed read accessors.

Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/mn10300/include/asm/io.h

@@ -67,6 +67,10 @@ static inline void writel(u32 b, volatile void __iomem *addr)
 #define __raw_writew writew
 #define __raw_writel writel
 
+#define writeb_relaxed writeb
+#define writew_relaxed writew
+#define writel_relaxed writel
+
 /*****************************************************************************/
 /*
  * traditional input/output functions