net: dsa: mv88e6xxx: rename the port vector member

Not all Marvell switch chips support port trunking, which is embedded in
the port vector data for ATU operations.

Rename the portv_trunkid member of the mv88e6xxx_atu_entry structure to
portvec to be more concise and consistent with the different chips.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>