net: Change return codes from net/eth.c to use errorno constants

Many functions returned -1 previously. Change them to return appropriate error
codes.

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
Reported-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
1 file changed