staging: comedi: pcmad: use comedi_range_is_bipolar()

Use the core provided helper function instead of duplicating it as
a private function.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/pcmad.c

@@ -75,12 +75,6 @@ static int pcmad_ai_wait_for_eoc(struct comedi_device *dev,
 	return -ETIME;
 }
 
-static bool pcmad_range_is_bipolar(struct comedi_subdevice *s,
-				   unsigned int range)
-{
-	return s->range_table->range[range].min < 0;
-}
-
 static int pcmad_ai_insn_read(struct comedi_device *dev,
 			      struct comedi_subdevice *s,
 			      struct comedi_insn *insn,
@@ -106,7 +100,7 @@ static int pcmad_ai_insn_read(struct comedi_device *dev,
 		if (s->maxdata == 0x0fff)
 			val >>= 4;
 
-		if (pcmad_range_is_bipolar(s, range)) {
+		if (comedi_range_is_bipolar(s, range)) {
 			/* munge the two's complement value */
 			val ^= ((s->maxdata + 1) >> 1);
 		}