Move irq_choose_cpu() into arch/powerpc/kernel/irq.c so that it can be used
by other PIC drivers.  The function is not MPIC-specific.
Signed-off-by: NStuart Yoder <stuart.yoder@freescale.com>
Signed-off-by: NTimur Tabi <timur@freescale.com>
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>