After commit 5bb578a0 ("ARM: 9298/1: Drop custom mdesc->handle_irq()")
the function icoll_handle_irq() is only used within irq-mxs.c.  So declare
it as static to fix the warning about a missing prototype when building
with W=1.
Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>