The mdio driver interface is generally useful for devices that require
MDIO without the full MII bus interface. This lifts the driver/interface
out of etherswitch(4), and adds a mdio(4) man page.
Submitted by: Landon Fuller <landon@landonf.org>
Differential Revision: https://reviews.freebsd.org/D4606
This fix the case when etherswitch is printing the information of port 0
vlan group (in port based vlan mode) with no member ports.
Add the ETHERSWITCH_VID_VALID support to ip17x driver.
Add the ETHERSWITCH_VID_VALID support to rt8366 driver.
arswitch doesn't need to be updated as it doesn't support vlans management
yet.
Approved by: adrian (mentor)
