WMI ready event gives the mac address, cache this
mac address in struct ath6kl so that it can be used to
compute the mac address for other vif in case of multi vif.
Signed-off-by: Vasanthakumar Thiagarajan <vthiagar@qca.qualcomm.com> Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>