staging: et131x: Bugfix - driver doesn't autoreneg after cable unplug/plug events

This driver has a long standing bug where removing and inserting the ethernet cable results in no packets being
trnasmitted / received and hence no autonegotiation occurring.

Fixed by resetting the rx/tx engines and queue on detecting a cable being removed.

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