mwl8k: Announce simultaneous AP-STA support on AP fw

Specify the STA support in iface_limit and
in wihpy->interface_modes

Signed-off-by: Yogesh Ashok Powar <yogeshp@marvell.com>
Signed-off-by: Nishant Sarmukadam <nishants@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>