netdrv: Fix unregister_netdev typos

Found during the (partial) unregister_netdevice audit that we didn't
have to have :)

It looks like a couple of Sun NIC drivers had unregister_netdevice
when they really meant unregister_netdev.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>