dabba: add speed,duplex,pause & autoneg settings.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>
dabba: refactor code to apply speed<->duplex mode.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>
dabba: remove link partner capabilities settings.

The link partner capabilites are advertisied by the interface at this
other side of the cable. Therefore dabbad cannot modify its status.
To have control over it, a dabbad instance needs to run on the link
partner and could set the advertised capabilities directly.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>
dabbad: link partner capabilities are read-only.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>