[PATCH] sis190: initialisation of MAC address.

Extract some mac addr code from SiS's driver.

Some magic may hide beyond the isa bridge. The Rx mac control
register is now set without condition.

Note: good or bad, this part of the code is quite close to sis900.c.

Signed-off-by: Francois Romieu <romieu@fr.zoreil.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>