irqchip/loongson-htvec: Check return value of irq_domain_translate_onecell()

Check the return value of irq_domain_translate_onecell() due to
it may returns -EINVAL if failed.

Fixes: 818e915f ("irqchip: Add Loongson HyperTransport Vector support")
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/1594087972-21715-5-git-send-email-yangtiezhu@loongson.cn