blackfin/irq: Use access helper irq_data_get_affinity_mask()

This is a preparatory patch for moving irq_data struct members.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Steven Miao <realmz6@gmail.com>
Cc: adi-buildroot-devel@lists.sourceforge.net
Link: http://lkml.kernel.org/r/20150713125611.652550580@linutronix.de


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