[PATCH] m32r: Fix "value computed not used" warnings

Fix to remove annoying gcc-4.1 warnings "value computed not used" for m32r;
Modify set_mb to cast to void for SMP.
Signed-off-by: Hirokazu Takata <takata@linux-m32r.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/asm-m32r/system.h

@@ -328,15 +328,15 @@ __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, int size)
 #define smp_rmb()	rmb()
 #define smp_wmb()	wmb()
 #define smp_read_barrier_depends()	read_barrier_depends()
+#define set_mb(var, value) do { (void) xchg(&var, value); } while (0)
 #else
 #define smp_mb()	barrier()
 #define smp_rmb()	barrier()
 #define smp_wmb()	barrier()
 #define smp_read_barrier_depends()	do { } while (0)
+#define set_mb(var, value) do { var = value; barrier(); } while (0)
 #endif
 
-#define set_mb(var, value) do { xchg(&var, value); } while (0)
-
 #define arch_align_stack(x) (x)
 
 #endif  /* _ASM_M32R_SYSTEM_H */