tlan: Enable link monitoring

Enable old link monitoring code and modify it:
 - control LINK LED
 - use separate timer so it does not interfere with ACT LED

Tested with Olicom OC-2326.

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: David S. Miller <davem@davemloft.net>