ath10k: fix static wep with more than 1 key in client mode

The default keyidx callback may be called after
more than 1 key is installed. This led to only 1
WEP key being reinstalled only. This caused Rxed
traffic encrypted with other WEP keys to be
dropped in client mode.

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