sh_eth: fix garbled TX error message

sh_eth_error() in case of a TX error tries to print a message using 2 dev_err()
calls with the first string not finished by '\n', so that the resulting message
would inevitably come out garbled, with something like "3net eth0: " inserted
in the middle.  Avoid that by merging 2 calls into one.

While at it, insert an empty line after the nearby declaration.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: David S. Miller <davem@davemloft.net>