hw/net: Fix the transmission return size

Fix the transmission return size because not all bytes could be
transmitted successfully. So, return a successful length instead of a
constant value.

Signed-off-by: Fea.Wang <fea.wang@sifive.com>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
Reviewed-by: Frank Chang <frank.chang@sifive.com>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
1 file changed