ath6kl: Initialize netdev hw_features for every interface

Move netdev->hw_features setting from ath6kl_core_init() to
init_netdev() so that it is done for every interface.

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