serial: icom: delete empty serial hooks

uart_ops::release_port() and uart_ops::request_port() are not required
by the serial layer. So no need to define empty ones.

Remove them.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220421085808.24152-10-jslaby@suse.cz


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