PCI: mediatek: Use helper function for_each_available_child_of_node_scoped()

The for_each_available_child_of_node_scoped() helper provides
a scope-based clean-up functionality to put the device_node
automatically, and as such, there is no need to call of_node_put()
directly.

Thus, use this helper to simplify the code.

Signed-off-by: Zhang Zekun <zhangzekun11@huawei.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20240831040413.126417-4-zhangzekun11@huawei.com


[kwilczynski: commit log]
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>