LoongArch: Define ARCH_IRQ_INIT_FLAGS as IRQ_NOPROBE

Currently we call irq_set_noprobe() in a loop for all IRQs, but indeed
it only works for IRQs below NR_IRQS_LEGACY because at init_IRQ() only
legacy interrupts have been allocated.

Instead, we can define ARCH_IRQ_INIT_FLAGS as IRQ_NOPROBE in asm/hwirq.h
and the core will automatically set the flag for all interrupts.

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Tianyang Zhang <zhangtianyang@loongson.cn>