staging: comedi: kcomedilib_main: (!foo) preferred over (foo == NULL)

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>

diff --cc drivers/staging/comedi/kcomedilib/kcomedilib_main.c
Simple merge