staging: comedi: icp_multi: rename static variable 'range_analog'

For aesthetics, rename this static variable so it has namespace
associated with the driver.

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>