mwifiex: fix incorrect ht capability problem

IEEE80211_CHAN_NO_HT40PLUS and IEEE80211_CHAN_NO_HT40PLUS channel
flags tell if HT40 operation is allowed on a channel or not.

This patch ensures ht_capability information is modified
accordingly so that we don't end up creating a HT40 connection
when it's not allowed for current regulatory domain.

Signed-off-by: Cathy Luo <cluo@marvell.com>
Signed-off-by: Ganapathi Bhat <gbhat@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>