powerpc/mpic: Make distribute_irqs obey MPIC_SINGLE_DEST_CPU

Previously we were setting an illegal configuration on mpc85xx
MPICs if CONFIG_IRQ_ALL_CPUS is enabled (which for some reason it is
in mpc85xx_smp_defconfig).
Signed-off-by: NScott Wood <scottwood@freescale.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/sysdev/mpic.c

@@ -54,7 +54,7 @@ static DEFINE_RAW_SPINLOCK(mpic_lock);
 
 #ifdef CONFIG_PPC32	/* XXX for now */
 #ifdef CONFIG_IRQ_ALL_CPUS
-#define distribute_irqs	(1)
+#define distribute_irqs	(!(mpic->flags & MPIC_SINGLE_DEST_CPU))
 #else
 #define distribute_irqs	(0)
 #endif