blackfin/irq: Use irq_set_handler_locked()

Use irq_set_handler_locked() as it avoids a redundant lookup of the
irq descriptor.

Search and update was done with coccinelle.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Steven Miao <realmz6@gmail.com>
Cc: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Julia Lawall <julia.lawall@lip6.fr>
Cc: adi-buildroot-devel@lists.sourceforge.net
Link: http://lkml.kernel.org/r/20150713125611.731615902@linutronix.de


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>