staging: vt6656: Fix crash when WLAN is turned off

Stop submitting urbs before calling usb_kill_urb() and usb_free_urb().

Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Link: https://lore.kernel.org/r/20220203192201.GA18509@matrix-ESPRIMO-P710


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>