net: ocpp: readonly is a bool.

GetConfiguration.conf read_only is a bool according to https://openchargealliance.org/wp-content/uploads/2025/04/OCPP_1.6_documentation.zip.

The Python OCPP implementation reports an error if read_only is reported as an integer: https://github.com/mobilityhouse/ocpp/blob/ae716a1507d708d83743d1132587cbb03522cda7/ocpp/v16/datatypes.py#L73

Signed-off-by: Markus Becker <markushx@gmail.com>