[POWERPC] IPIC: Fix spinlock recursion in set_irq_handler

This causes ipic_set_irq_type to set the handler directly rather
than call set_irq_handler, which causes spinlock recursion because
the lock is already held when ipic_set_irq_type is called.

I'm also not convinced that ipic_set_irq_type should be changing the
handler at all.  There seem to be several controllers that don't and
several that do.  Those that do would break what appears to be a common
usage of calling set_irq_chip_and_handler followed by set_irq_type, if a
non-standard handler were to be used.  OTOH, irq_create_of_mapping()
doesn't set the handler, but only calls set_irq_type().

This patch gets things working in the spinlock-debugging-enabled case,
but I'm curious as to where the handler setting is ideally supposed to be
done.  I don't see any documentation on set_irq_type() that clarifies
what the semantics are supposed to be.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>