Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Add a new flag (ETHERSWITCH_VID_VALID) to say what vlangroups are in use.
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)

Bring in a basic ethernet switch driver for the IP17x series of
switches.

These are notably found on some AR71xx based Mikrotik boards.

Submitted by: Luiz Otavio O Souza <loos.br@gmail.com>
Reviewed by: ray