serial: icom: remove unused struct icom_port members

Some members of struct icom_port are completely unused or only set and
never read. Remove all those.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220421085808.24152-11-jslaby@suse.cz


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