PCI: Hold the rescan mutex when scanning for the first time

With the introduction of PCI device power control drivers that will be
able to trigger the port rescan when probing, we need to hold the rescan
mutex during the initial pci_host_probe() too or the two could get in
each other's way.

Tested-by: Amit Pundir <amit.pundir@linaro.org>
Tested-by: Neil Armstrong <neil.armstrong@linaro.org> # on SM8550-QRD, SM8650-QRD & SM8650-HDK
Tested-by: Caleb Connolly <caleb.connolly@linaro.org> # OnePlus 8T
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20240612082019.19161-2-brgl@bgdev.pl


Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>