gpio: tqmx86: fix uninitialized variable girq

The commit 92461060 ("gpio: tpmx86: Move PM device over to
irq domain") adds a dereference of girq that may be uninitialized.

Fix this by moving irq_domain_set_pm_device into if true branch
as suggested by Marc Zyngier.

Fixes: 92461060

 ("gpio: tpmx86: Move PM device over to irq domain")
Suggested-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>