mwifiex: handle interface type changes correctly

mlan0: managed or ibss
The iftype can be changed from STATION to ADHOC, and vice versa.

uap0: AP only
The iftype cannot be changed.

Signed-off-by: Avinash Patil <patila@marvell.com>
Signed-off-by: Yogesh Ashok Powar <yogeshp@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>