usb: fail on usb_hub_create_port_device() errors

Ignoring usb_hub_create_port_device() errors cause later NULL pointer
deference when uninitialized hub->ports[i] entries are dereferenced
after port memory allocation error.

Signed-off-by: Krzysztof Mazur <krzysiek@podlesie.net>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>