parisc: io: implement dummy relaxed accessor macros for writes

write{b,w,l,q}_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 parisc, in the
same vein as the dummy definitions for the relaxed read accessors.

Cc: Helge Deller <deller@gmx.de>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/parisc/include/asm/io.h

@@ -221,6 +221,10 @@ static inline void writeq(unsigned long long q, volatile void __iomem *addr)
 #define readw_relaxed(addr)	readw(addr)
 #define readl_relaxed(addr)	readl(addr)
 #define readq_relaxed(addr)	readq(addr)
+#define writeb_relaxed(b, addr)	writeb(b, addr)
+#define writew_relaxed(w, addr)	writew(w, addr)
+#define writel_relaxed(l, addr)	writel(l, addr)
+#define writeq_relaxed(q, addr)	writeq(q, addr)
 
 #define mmiowb() do { } while (0)