tty: isicom, remove this orphan

The Isicom driver was orphaned by commit d86b3001 (MAINTAINERS:
orphan isicom) 10 years ago. Noone stepped up to take care of them and
to fix all the issues the driver has.

So it's time to drop the driver with all its traces.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210302062214.29627-6-jslaby@suse.cz


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