net: netcp: ethss: k2g: add promiscuous mode support

This patch adds support for promiscuous mode in k2g's network
driver. When upper layer instructs to transition from
non-promiscuous mode to promiscuous mode or vice versa
K2G network driver needs to configure ALE accordingly
so that in case of non-promiscuous mode, ALE will not flood
all unicast packets to host port, while in promiscuous
mode, it will pass all received unicast packets to
host port.

Signed-off-by: WingMan Kwok <w-kwok2@ti.com>
Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>