MIPS: define write{b,w,l,q}_relaxed

MIPS does define read{b,w,l,q}_relaxed but does not define their write
counterparts: write{b,w,l,q}_relaxed. This patch adds the missing
definitions for the write*_relaxed I/O accessors.
Signed-off-by: NFlorian Fainelli <f.fainelli@gmail.com>
Acked-by: NJohn Crispin <blogic@openwrt.org>
Cc: linux-mips@linux-mips.org
Cc: cernekee@gmail.com
Cc: jogo@openwrt.org
Patchwork: https://patchwork.linux-mips.org/patch/5352/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/io.h

@@ -454,6 +454,11 @@ __BUILDIO(q, u64)
 #define readl_relaxed			readl
 #define readq_relaxed			readq
 
+#define writeb_relaxed			writeb
+#define writew_relaxed			writew
+#define writel_relaxed			writel
+#define writeq_relaxed			writeq
+
 #define readb_be(addr)							\
 	__raw_readb((__force unsigned *)(addr))
 #define readw_be(addr)							\