PCI/pwrctl: Remove pwrctl device without iterating over all children of pwrctl parent

There is no need to iterate over all children of the pwrctl device parent
to remove the pwrctl device. Since the pwrctl device associated with the
PCI device can be found using of_find_device_by_node() API, use it directly
instead.

Any pwrctl devices lying around without getting associated with the PCI
devices will be removed once their parent device gets removed.

Link: https://lore.kernel.org/r/20241025-pci-pwrctl-rework-v2-5-568756156cbe@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>
[bhelgaas: commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>