usbip: vhci_hcd: check rhport before using in vhci_hub_control()

Validate !rhport < 0 before using it to access port_status array.

Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>