[PATCH] sundance: use NULL for pointer

Use NULL instead of 0 for pointers (cures sparse warnings).

drivers/net/sundance.c:1106:16: warning: Using plain integer as NULL pointer
drivers/net/sundance.c:1652:16: warning: Using plain integer as NULL pointer

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>