powerpc:eVh_pic: Kill irq_desc abuse

I'm really grumpy about this one. The line:

#include "../../../kernel/irq/settings.h"

should have been an alarm sign for all people who added their SOB to
this trainwreck.

When I cleaned up the mess people made with interrupt descriptors a
few years ago, I warned that I'm going to hunt down new offenders and
treat them with stinking trouts. In this case I'll use frozen shark
for a better educational value.

The whole idiocy which was done there could have been avoided with two
lines of perfectly fine code. And do not complain about the lack of
correct examples in tree.

The solution is simple:

  Remove the brainfart and use the proper functions, which should
  have been used in the first place

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Ashish Kalra <ashish.kalra@freescale.com>
Cc: Timur Tabi <timur@freescale.com>
Cc: Kumar Gala <galak@kernel.crashing.org>
Cc: ppc <linuxppc-dev@lists.ozlabs.org>
Link: http://lkml.kernel.org/r/20140223212736.451970660@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>