staging: et131x: Add auto-negotiation and 1000BT_Half as supported protocols

The driver supports auto-negotiation and 100BaetT_Half but doesn't
advertise or list it in it's phydev. Fix that.

Signed-off-by: Mark Einon <mark.einon@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>