When user wants to add a station interface when
AP firmware is loaded & in-use, allow creating
it and also notify user about the same.

Allow adding max one STA interface for AP fw.
Signed-off-by: NYogesh Ashok Powar <yogeshp@marvell.com>
Signed-off-by: NNishant Sarmukadam <nishants@marvell.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>