arm: omap: Fix typo in ams-delta-fiq.c

8435cf75 (arm: Replace various irq_desc accesses) typoed
irq_get_irq_chip() instead of irq_get_chip().

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>