Return 0 in case of log-dump executed successfully in cli
Return 0 in case of log-dump executed successfully in cli

Switchtec lib API:switchtec_log_to_file return the total length
of the log fetched in case of successful. But for cli, it is
better to return 0 in that case, which align with other cli
commands. Change it accordingly.

Signed-off-by: Wesley Sheng <2dd9bb739c19413d08ba3d30d3b08863544ccf6b@microchip.com>

Microsemi/switchtec-user,Microsemi/switchtec-user