Because of the hardware recovery mechanism, its possible the
__wl1271_op_remove_interface is called twice. Currently, this leads to a
kernel crash even before a kernel WARNing can be issued.

Fix this.
Signed-off-by: NJuuso Oikarinen <juuso.oikarinen@nokia.com>
Signed-off-by: NLuciano Coelho <coelho@ti.com>