Fix a boot regression in existing kernels causing:

genirq: Threaded irq requested with handler=NULL and !ONESHOT for irq XXX

caused by 1c6c6952 (genirq: Reject bogus threaded irq requests).
Signed-off-by: NHeiko Stuebner <heiko@sntech.de>
Signed-off-by: NChris Ball <cjb@laptop.org>