PCI/pwrctl: Use of_platform_device_create() to create pwrctl devices

The of_platform_populate() API creates platform devices by descending
through the children of the parent node. But it provides no control over
the child nodes, which makes it difficult to add checks for the child
nodes in the future.

Use of_platform_device_create() and for_each_child_of_node_scoped() to make
it possible to add checks for each node before creating the platform
device.

Link: https://lore.kernel.org/r/20241025-pci-pwrctl-rework-v2-1-568756156cbe@linaro.org


Tested-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Tested-by: Krishna chaitanya chundru <quic_krichai@quicinc.com>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>