[PATCH] sk98lin: fix truncated collision threshold mask

Patch to correct broken collision threshold mask in (same problem
as sky2 driver).  Should be three bits wide, but the mask only allows
for 1 bit to be set.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>