platform/chrome: cros_ec_proto: separate cros_ec_get_proto_info_legacy()

Rename cros_ec_host_command_proto_query_v2() to
cros_ec_get_proto_info_legacy() and make it responsible for setting
`ec_dev` fields for EC protocol v2.

Reviewed-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
Link: https://lore.kernel.org/r/20220609084957.3684698-11-tzungbi@kernel.org