powerpc: Drop return value of smp_ops->probe()

smp_ops->probe() is currently supposed to return the number of cpus in
the system.

The last actual usage of the value was removed in May 2007 in e147ec8f1808
"[POWERPC] Simplify smp_space_timers". We still passed the value around
until June 2010 when even that was finally removed in c1aa687d499a
"powerpc: Clean up obsolete code relating to decrementer and timebase".

So drop that requirement, probe() now returns void, and update all
implementations.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/sysdev/mpic.c b/arch/powerpc/sysdev/mpic.c
index fb19084..b2b8447 100644
--- a/arch/powerpc/sysdev/mpic.c
+++ b/arch/powerpc/sysdev/mpic.c
@@ -1897,7 +1897,7 @@
 		       msg * MPIC_INFO(CPU_IPI_DISPATCH_STRIDE), physmask);
 }
 
-int __init smp_mpic_probe(void)
+void __init smp_mpic_probe(void)
 {
 	int nr_cpus;
 
@@ -1909,8 +1909,6 @@
 
 	if (nr_cpus > 1)
 		mpic_request_ipis();
-
-	return nr_cpus;
 }
 
 void smp_mpic_setup_cpu(int cpu)