net: ethernet: mvneta: Remove IFF_UNICAST_FLT which is not implemented

The mvneta driver advertises it supports IFF_UNICAST_FLT. However, it
actually does not. The hardware probably does support it, but there is
no code to configure the filter. As a quick and simple fix, remove the
flag. This will cause the core to fall back to promiscuous mode.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Fixes: b50b72de ("net: mvneta: enable features before registering the driver")
Signed-off-by: David S. Miller <davem@davemloft.net>