Fix missing unlock before return from function macb_start_xmit()
in the error handling case.
Fixes: 007e4ba3ee13 ("net: macb: initialize checksum when using
checksum offloading") Signed-off-by: Wei Yongjun <[email protected]> Acked-by: Nicolas Ferre <[email protected]> Signed-off-by: David S. Miller <[email protected]>