FST L2DA simplification

Starting from this change, the L2DA mux module distinguishes between AP
and STA that allows it to act in accordance to hostap type.

For STA, it configures bond L2DA to de-duplicate the RX, but doesn't
enable TX MC duplication anymore. Instead, it uses L2DA default_slave
to route all the traffic via the desired interface.

For AP, it configures bond L2DA to duplicate TX MC traffic, while it
disables the RX de-duplication, as STA doesn't duplicate packets
anymore.

Change-Id: I89eff72faeb3df0772d6ebe89dee650583a0b1de