ath6kl: Fix static WEP configuration in AP mode

Configuration of the WEP keys needs to be delayed until the AP mode has
been properly started at the target. Partial support for delaying the
WEP key configuration was already in place in the driver, but the actual
part of deciding when to do this was missing.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>