mwl8k: set mac type to MWL8K_MAC_TYPE_SECONDARY_CLIENT

Set mac type for station interface on AP firmware
as secondary. This allows the firmware to set specific
characteristics for the STA interface.

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>