staging: vchi: Get rid of vchi_service_set_option()

There are no users for that function.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Link: https://lore.kernel.org/r/20200527115400.31391-6-nsaenzjulienne@suse.de


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