cmd: return code when tlv_eeprom incorrectly called

A command called with incorrect parameters should set $? to 1 (false).
Instead of calling cmd_usage(cmdtp) and then returning 0 just return
CMD_RET_FAILURE.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Acked-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: Stefan Roese <sr@denx.de>