PCI: endpoint: Don't stop controller when unbinding endpoint function

Unbinding an endpoint function from the endpoint controller shouldn't stop
the controller.  This is especially a problem for multi-function endpoints
where other endpoints may still be active.

Don't stop the controller when unbinding one of its endpoints.  Normally
the controller is stopped via configfs.

Fixes: 349e7a85 ("PCI: endpoint: functions: Add an EP function to test PCI")
Link: https://lore.kernel.org/r/20220622040924.113279-1-mie@igel.co.jp


Signed-off-by: Shunsuke Mie <mie@igel.co.jp>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Kishon Vijay Abraham I <kishon@ti.com>