enable 10/100M at VSC8601 at tsec driver

Currently VSC8601 doesn't link with 10/100M partners if the
EEPROM/Strapping is not set up.
Setting the auto-neg register fixes this.

Signed-off-by: Andre Schwarz <andre.schwarz@matrix-vision.de>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>