arm64: dts: marvell: 8040-db: enable the SFP ports

This patch enables the SFP ports on the Armada 8040 DB as these ports
are now supported by the PPv2 driver (since the PHY is now optional).

Signed-off-by: Antoine Tenart <antoine.tenart@free-electrons.com>
Tested-by: Marcin Wojtas <mw@semihalf.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>