arm64: Allow forced irq threading

Now its safe to allow forced interrupt threading for arm64,
all timer interrupts and the perf interrupt are marked NO_THREAD, as is
the case with arch/arm: da0ec6f7

 ARM: 7814/2: Allow forced irq threading

Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Suggested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>