Staging: comedi: do not initialise statics to 0 or NULL

This is a patch to adv_pci_dio.c that fixes an error initializing

static struct pci_dio_private *pci_priv to NULL

removed the initialization.
found by the checkpatch.pl tool.
Signed-off-by: Mariano Guerra <luismarianoguerra@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/comedi/drivers/adv_pci_dio.c

@@ -422,7 +422,7 @@ struct pci_dio_private {
 	unsigned short IDIFiltrHigh[8];	/*  IDI's filter value high signal */
 };
 
-static struct pci_dio_private *pci_priv = NULL;	/* list of allocated cards */
+static struct pci_dio_private *pci_priv;	/* list of allocated cards */
 
 #define devpriv ((struct pci_dio_private *)dev->private)
 #define this_board ((const struct dio_boardtype *)dev->board_ptr)