mwifiex: store AP configuration in private structure

Store AP configuration in private structure so that we know
current AP configuration.

Signed-off-by: Avinash Patil <patila@marvell.com>
Signed-off-by: Qingshui Gao <gaoqs@marvell.com>
Signed-off-by: Cathy Luo <cluo@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>