We can stop trying according to try_number now and do not need to use
root_bus checking as stop sign.
In extreme case we could need to reallocate resource for device just
under root bus. For PCI root bus hot-add, we need to retry to assign
resources to PCI devices just under pci root bus.
Signed-off-by: Yinghai Lu <yinghai@kernel.org> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>