staging: comedi: drivers: ni_mio_common: add names to function pointer parameters.

Checkpatch.pl complains about packbits function pointer that lacks
parameters name.

Add parameter names to packbits function pointer.
Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/ni_mio_common.c

@@ -4294,7 +4294,7 @@ static int pack_ad8842(int addr, int val, int *bitstring)
 struct caldac_struct {
 	int n_chans;
 	int n_bits;
-	int (*packbits)(int, int, int *);
+	int (*packbits)(int address, int value, int *bitstring);
 };
 
 static struct caldac_struct caldacs[] = {