powerpc: 52xx: provide a default in mpc52xx_irqhost_map()

My gcc-4.3.5 fails to compile due to:

|cc1: warnings being treated as errors
|arch/powerpc/platforms/52xx/mpc52xx_pic.c: In function ‘mpc52xx_irqhost_map’:
|arch/powerpc/platforms/52xx/mpc52xx_pic.c:343: error: ‘irqchip’ may be used uninitialized in this function

since commit e34298c ("powerpc: 52xx: nop out unsupported critical
IRQs"). This warning is complete crap since only values 0…3 are possible
which are checked but gcc fails to understand that. I wouldn't care much
but since this is compiled with -Werror I made this patch.
While add it, I replaced the warning from l2irq to l1irq since this is
the number that is evaluated.

Signed-off-by: Sebastian Andrzej Siewior <[e-mail]>
Signed-off-by: Anatolij Gustschin <[e-mail]>

arch/powerpc/platforms/52xx/mpc52xx_pic.c

···
 	case MPC52xx_IRQ_L1_PERP: irqchip = &mpc52xx_periph_irqchip; break;
 	case MPC52xx_IRQ_L1_SDMA: irqchip = &mpc52xx_sdma_irqchip; break;
 	case MPC52xx_IRQ_L1_CRIT:
+	default:
 		pr_warn("%s: Critical IRQ #%d is unsupported! Nopping it.\n",
-			__func__, l2irq);
+			__func__, l1irq);
 		irq_set_chip(virq, &no_irq_chip);
 		return 0;
 	}