mwifiex: fix bandwidth display problem

Instead of using HT info from beacon IEs, use HT info from
association response frame to update bandwidth in
cfg80211_get_channel handler.

Signed-off-by: Nachiket Kukade <kukaden@marvell.com>
Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>