PCI/pwrctrl: Move pci_pwrctrl_unregister() to pci_destroy_dev()

PCI/pwrctrl: Move pci_pwrctrl_unregister() to pci_destroy_dev()

The PCI core will try to access the devices even after pci_stop_dev()
for things like Data Object Exchange (DOE), ASPM, etc.

So, move pci_pwrctrl_unregister() to the near end of pci_destroy_dev()
to make sure that the devices are powered down only after the PCI core
is done with them.

Suggested-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Lukas Wunner <lukas@wunner.de>
Tested-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20250116-pci-pwrctrl-slot-v3-2-827473c8fbf4@linaro.org
[kwilczynski: commit log]
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>