mwl8k: Do not call STA specific cmds not supported by the AP fw

While using STA mode in the AP firmware, avoid
calling some firmware commands which are not
supported by the AP firmware.

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>