mxser_port->opmode_ioaddr is initialized only for MOXA_MUST_MU860_HWID
chips, but no precautions have been undertaken to prevent reading and
writing to undefined port number.
Signed-off-by: NMatwey V. Kornilov <matwey@sai.msu.ru>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>