[PATCH] fix gcc-3.4 warning in percpu code

From: Rusty Russell <rusty@rustcorp.com.au>

It's complaining about:

#define per_cpu(var, cpu)			((void)cpu, per_cpu__##var)

There are several ways of fixing this, but the simplest is:

#define per_cpu(var, cpu)			(*((void)cpu, &per_cpu__##var))

include/asm-generic/percpu.h

@@ -29,7 +29,7 @@ do {								\
 #define DEFINE_PER_CPU(type, name) \
     __typeof__(type) per_cpu__##name
 
-#define per_cpu(var, cpu)			((void)cpu, per_cpu__##var)
+#define per_cpu(var, cpu)			(*((void)cpu, &per_cpu__##var))
 #define __get_cpu_var(var)			per_cpu__##var
 
 #endif	/* SMP */