net: ftmac100: handle netdev flags IFF_PROMISC and IFF_ALLMULTI

When netdev->flags has IFF_PROMISC or IFF_ALLMULTI, set the
corresponding bits in the MAC Control Register (MACCR).

This change is based on code from the ftgmac100 driver, see
ftgmac100_start_hw() in ftgmac100.c

Signed-off-by: Sergei Antonov <saproj@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>