[PATCH precise] powerpc/pmac: Fix SMP kernels on pre-core99 UP machines

[Jeremy Kerr]

From: Benjamin Herrenschmidt <benh at kernel.crashing.org>

BugLink: https://bugs.launchpad.net/bugs/959959

The code for "powersurge" SMP would kick in and cause a crash
at boot due to the lack of a NULL test.

Signed-off-by: Benjamin Herrenschmidt <benh at kernel.crashing.org>
Signed-off-by: Jeremy Kerr <jeremy.kerr at canonical.com>
Reported-By: Adam Conrad <adconrad at ubuntu.com>
Tested-By: Adam Conrad <adconrad at ubuntu.com>

Cherry-picked from upstream commit
78c5c68a4cf4329d17abfa469345ddf323d4fd62

---
 arch/powerpc/platforms/powermac/smp.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/powermac/smp.c b/arch/powerpc/platforms/powermac/smp.c
index 9b6a820..3394254 100644
--- a/arch/powerpc/platforms/powermac/smp.c
+++ b/arch/powerpc/platforms/powermac/smp.c
@@ -414,7 +414,7 @@ static struct irqaction psurge_irqaction = {
 
 static void __init smp_psurge_setup_cpu(int cpu_nr)
 {
-	if (cpu_nr != 0)
+	if (cpu_nr != 0 || !psurge_start)
 		return;
 
 	/* reset the entry point so if we get another intr we won't