Staging: comedi: Fix code style in jr3_pci.c

Static variables are initialised to 0 by GCC.
Fixes checkpatch.pl error:
  ERROR: do not initialise statics to 0 or NULL
  #684: FILE: jr3_pci.c:684:
  +	static const struct jr3_pci_board *board = NULL;
Signed-off-by: Vladimir A. Nazarenko <naszar@ya.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/jr3_pci.c

@@ -681,7 +681,7 @@ static int jr3_pci_auto_attach(struct comedi_device *dev,
 			       unsigned long context)
 {
 	struct pci_dev *pcidev = comedi_to_pci_dev(dev);
-	static const struct jr3_pci_board *board = NULL;
+	static const struct jr3_pci_board *board;
 	struct jr3_pci_dev_private *devpriv;
 	struct jr3_pci_subdev_private *spriv;
 	struct comedi_subdevice *s;