staging: comedi: icp_multi: remove check_channel_list()

This function would only be needed in the driver supported async
commands. It's #if 0'ed out anyway so just remove it.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>