ath10k: remove unnecessary checks

mac80211 interface iteration functions that were
used originally iterated over interfaces that
weren't re-added to the driver during recovery.

Since internal vif list is now used it's safe to
remove the safe-guard as internal vif list is
based on add/remove_interface function which
guarantees that vdev is created in FW before it is
iterated over.

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