lcs: invalid return codes from hard_start_xmit.

Lcs hard_start_xmit routine issued return codes other than
defined for this interface. Now lcs returns only either
NETDEV_TX_OK or NETDEV_TX_BUSY.

Signed-off-by: Klaus-Dieter Wacker <kdwacker@de.ibm.com>
Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>