spidernet: add missing initialization

This patch fixes initialization of "aneg_count" and "medium" fields in
spider_net_card to make spidernet driver correctly sets "link status".

Signed-off-by: Kou Ishizaki <kou.ishizaki@toshiba.co.jp>
Acked-by: Jens Osterkamp <jens@de.ibm.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>