[POWERPC] Fix setting of irq trigger type in UIC driver

The UIC (interrupt controller in 4xx embedded CPUs) driver currently
missets the IRQ_lEVEL flag in desc->status, due to a thinko.  This
patch fixes the bug.

Currently this is only a cosmetic problem (affects the output in
/proc/interrupts), however subsequent patches will use the IRQ_LEVEL
flag to affect flow handling.

Signed-off-by: Valentine Barshak <vbarshak@ru.mvista.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Acked-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>