ARM: 7814/2: Allow forced irq threading

All timer interrupts and the perf interrupt are marked NO_THREAD, so
its safe to allow forced interrupt threading.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>