mwifiex: set HT capability based on cfg80211_ap_settings

Parse HT IE from cfg80211 and set HT capabilities accordingly
to FW. If HT IE is missing, 11n would be disabled in FW.

Signed-off-by: Avinash Patil <patila@marvell.com>
Signed-off-by: Kiran Divekar <dkiran@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>