If something failed along add_interface() setup it
was possible to leak a vdev id, vdev and peer.

This could end up with leaked FW state or FW crash
(assuming add_interface() failure wasn't a result of
a crash).

kvalo: rebased, whitespace fixes
Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>