Move adding station to add_interface

Moving adding station to add_interface because this is where it must be.
Also distinguish between AP and Station mode

Signed-off-by: Eugene Krasnikov <k.eugene.e@gmail.com>
Print out error message in case SMD command fails

This helps debugging driver

Signed-off-by: Eugene Krasnikov <k.eugene.e@gmail.com>
Initial commit for AP mode support

To support AP wcn36xx must send 2 SMD commands:
CONFIG_BSS - to config hw to be in AP mode
SEND_BEACON – start sending beacons according to template

Signed-off-by: Eugene Krasnikov <k.eugene.e@gmail.com>