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 support for 802.1q and port based vlans for arswitch.

Tested on: RB450G (standalone ar8316), RSPRO (standalone ar8316) and
TPLink MR-3220 (ar724x integrated switch).

Approved by: adrian (mentor)
Obtained from: zrouter

Fix the arswitch instability problem. It turns out that the
arswitch_writereg() routine was writing the registers in the wrong order.

Revert -r241918 as the root problem is now fixed. Remove another workaround
from arswitch_ar7240.c.

Simplify and fix the code on arswitch_writephy() by using
arswitch_writereg().

While here remove a redundant declaration from arswitchvar.h.

Approved by: adrian (mentor)

Setup the CPU port and broadcast map on the AR7240, rather than
depending upon the bootloader initialising it.

The aim is to eventually support a full switch set and reinitialisation
rather than relying on a consistent bootloader setup.

Remove the port flood config from arswitch.c, it's not yet used and
it's totally incorrect.

Whilst I'm here, also add in a comment describing why the full switch
reset is disabled.

Obtained from: Linux (OpenWRT) - Values

.. oops, include setting the MTU.

* Remove the AR7240 register defines and reuse the AR8x16 defines.
* Include a new register define to represent "disable port mirroring
to CPU port".

Obtained from: Patrick Kelsey <kelsey@ieee.org>

Further arswitch work:

* Add in the AR724x support. It probes the same as an AR8216/AR8316, so
just add in a hint to force the probe success rather than auto-detecting
it.

* Add in the missing entries from conf/files, lacking in the previous
commit.

The register values and CPU port / mirror port initialisation value was
obtained from Linux OpenWRT ag71xx_ar7240.c.

The DELAY(1000) to let things settle is my local workaround. For some
reason, PHY4 doesn't seem to probe very reliably without it. It's quite
possible that we're missing some MDIO bus initialisation code in if_arge
for the AR724x case. As I dislike DELAY() workarounds in general, it's
definitely worth trying to figure out why this is the case.

Tested on: AP93 (AR7240) reference design

Obtained from: Linux OpenWRT