mxser: remove pointless ioaddr checks

struct mxser_port::ioaddr can never be NULL once set in ->probe. Hence
the checks for it are pointless. Remove them.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210618061516.662-55-jslaby@suse.cz


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>