mwifiex: channel switch handling for station

After receiving channel switch announcement from AP, scan and
association on that channel is blocked for DFS_CHAN_MOVE_TIME
(10 seconds). Hence station will be able to connect to the AP,
once it is moved to new channel.

Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: Paul Stewart <pstew@chromium.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>