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>