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

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

Add the ability to change the vlan operation mode.

This adds a vlan capability field to etherswitch_info structure and some
definitions of ports flags.

It adds the support to global config parameters which right now is used
only to switch between the vlan modes, but it is intended to be extended
to support the setup of others parameters (STP, mirror, etc.).

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

Locking for etherswitch framework:
* add lock/unlock methods;
* add lock/unlock default implementation;
* surround switch IOCTLs with locking;
* add lock/unlock implementation for arswitch;

Submitted by: Luiz Otavio O Souza
Approved by: adrian (mentor)

Commit the first pass of the etherswitch support.

This is designed to support the very basic ethernet switch chip behaviour,
specifically:

* accessing switch register space;
* accessing per-PHY registers (for switches that actually expose PHYs);
* basic vlan group support, which applies for the rtl8366 driver but not
for the atheros switches.

This also includes initial support for:

* rtl8366rb support - which is a 10/100/1000 switch which supports
vlan groups;
* Initial Atheros AR8316 switch support - which is a 10/100/1000 switch
which supports an alternate vlan configuration (so the vlan group
methods are stubbed.)

The general idea here is that the switch driver may speak to a variety of
backend busses (mdio, i2c, spi, whatever) and expose:

* If applicable, one or more MDIO busses which ethernet interfaces can
then attach PHYs to via miiproxy/mdioproxy;

* exposes miibusses, one for each port at the moment, so ..

* .. a PHY can be exposed on each miibus, for each switch port, with all
of the existing MII/ifnet framework.

However:

* The ifnet is manually created for now, and it isn't linked into the
interface list, nor can you (currently) send/receive frames on this ifnet.
At some point in the future there may be _some_ support for this, for
switches with a multi-port, isolated mode.

* I'm still in the process of sorting out correct(er) locking.

TODO:

* ray's switch code in zrouter (zrouter.org) includes a much more developed
newbus API that covers the various switch methods, as well as a
capability API so drivers, the switch layer and the userland utility
can properly control the subset of supported features.

The plan is to sort that out later, once the rest of ray's switch drivers
are brought over and extended to export MII busses and PHYs.

Submitted by: Stefan Bethke <stb@lassitu.de>
Reviewed by: ray