net: mvpp2: remove unused 'has_phy' field

The 'has_phy' field from struct mvpp2_port is no longer used.
Remove it.

Signed-off-by: Marcin Wojtas <mw@semihalf.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>