drivers: net: use NETDEV_TX_OK instead of NETDEV_TX_LOCKED

These drivers already call netif_stop_queue() so we should not be called
unless tx space is available.  Just free the skb and return TX_OK.

Followup patch will remove NETDEV_TX_LOCKED from the kernel.

Cc: linux-parisc@vger.kernel.org
Cc: linux-hams@vger.kernel.org
Cc: Thomas Sailer <t.sailer@alumni.ethz.ch>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>