gpio: xgene-sb: Use irq_domain_free_irqs_common()

Current code calls irq_domain_alloc_irqs_parent() in .alloc,
so it should call irq_domain_free_irqs_parent() accordingly in .free.
Fix it by switching to use irq_domain_free_irqs_common() instead.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>