irqchip: spear_shirq: Simplify chained handler

I don't know if there are less efficient ways to code that. Get rid of
the loop mess and use efficient code.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20140619212713.662897061@linutronix.de


Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>