staging: comedi: allow it to be built-in

There is no particular reason why comedi has to be built as kernel
modules.  Remove the `depends on m` from the Kconfig file to allow it to
be built-in.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>