iio: proximity: sx9500: Fix proximity value

Because of the ABI confusion proximity value exposed by SX9500
was inverted.
Signed-off-by: NDaniel Baluta <daniel.baluta@intel.com>
Reviewed-by: NVlad Dogaru <vlad.dogaru@intel.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

drivers/iio/proximity/sx9500.c

@@ -281,7 +281,7 @@ static int sx9500_read_prox_data(struct sx9500_data *data,
 	if (ret < 0)
 		return ret;
 
-	*val = 32767 - (s16)be16_to_cpu(regval);
+	*val = be16_to_cpu(regval);
 
 	return IIO_VAL_INT;
 }