ath6kl: Make sure wiphy is registered before calling regulatory_hint()

As regulatory events are processed even before the wiphy is registered,
calling regulatory_hint() at early stage should be fixed.

Signed-off-by: Vasanthakumar Thiagarajan <vthiagar@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>