ath6kl: Fix wrong regulatory domain disconnection.

One minute after a successful connection, the kernel checks if the
frequency and the channel width are well configured for the country we
are in. (regulatory domain)

ath6kl driver was setting the NL80211_CHAN_HT20 channel without checking
for the HT capabilities. (we should have NL80211_CHAN_NO_HT in our
case because the firmware did not support HT)

This patch adds a check on ht_cap.ht_supported in order to create the
channel corresponding to the firmware capabilities.

Signed-off-by: Pierre Le Magourou <plemagourou@aldebaran.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>