irq: set_irq_chip() has redundant call to irq_to_desc()

Extraneous call to irq_to_desc().
Signed-off-by: NDean Nelson <dcn@sgi.com>
Cc: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

kernel/irq/chip.c

@@ -102,7 +102,6 @@ int set_irq_chip(unsigned int irq, struct irq_chip *chip)
 	if (!chip)
 		chip = &no_irq_chip;
 
-	desc = irq_to_desc(irq);
 	spin_lock_irqsave(&desc->lock, flags);
 	irq_chip_set_defaults(chip);
 	desc->chip = chip;