Staging: comedi: fix initialise statics to 0 or NULL issue in cb_das16_cs.c

This is a patch to the cb_das16_cs.c file that fixes up a initialise
statics to 0 or NULL warning found by the checkpatch.pl tool.
Signed-off-by: NRavishankar Karkala Mallikarjunayya <ravishankar.km@greenturtles.in>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/staging/comedi/drivers/cb_das16_cs.c

@@ -99,7 +99,7 @@ static struct comedi_driver driver_das16cs = {
 	.detach = das16cs_detach,
 };
 
-static struct pcmcia_device *cur_dev = NULL;
+static struct pcmcia_device *cur_dev;
 
 static const struct comedi_lrange das16cs_ai_range = { 4, {
 							   RANGE(-10, 10),