arm64: use SOFTIRQ_ON_OWN_STACK for enabling softirq stack

For those architectures with HAVE_SOFTIRQ_ON_OWN_STACK use
their dedicated softirq stack when !PREEMPT_RT. This condition
is ensured by SOFTIRQ_ON_OWN_STACK.

Let arm64 use SOFTIRQ_ON_OWN_STACK as well to select its
usage of the stack.

Signed-off-by: Ryo Takakura <ryotkkr98@gmail.com>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Author: Ryo Takakura

arch/arm64/kernel/irq.c

@@ -62,7 +62,7 @@ static void __init init_irq_stacks(void)
 	}
 }
 
-#ifndef CONFIG_PREEMPT_RT
+#ifdef CONFIG_SOFTIRQ_ON_OWN_STACK
 static void ____do_softirq(struct pt_regs *regs)
 {
 	__do_softirq();