irqchip: spear_shirq: Namespace cleanup

The struct members of the shirq block struct are named to confuse the
hell out of the casual reader. Clean it up.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20140619212713.219411832@linutronix.de
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>