mwifiex: advertise multichannel support to cfg80211

This patch adds support to advetise mwifiex multichannel support to
cfg80211. If module parameter drcs is enabled and FW supports multichannel
operation we advertise this support to cfg80211. As of now 2 simultaneous
channels are supported.

Signed-off-by: Avinash Patil <patila@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>