iio: mxs-lradc: convert is_divided to a bitmap

mxs_lradc.is_divided was an unsigned long array. Convert it to a bitmap to save
some memory.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/adc/mxs-lradc.c

@@ -211,7 +211,7 @@ struct mxs_lradc {
 
 	const uint32_t		*vref_mv;
 	struct mxs_lradc_scale	scale_avail[LRADC_MAX_TOTAL_CHANS][2];
-	unsigned int		is_divided[LRADC_MAX_TOTAL_CHANS];
+	unsigned long		is_divided;
 
 	/*
 	 * Touchscreen LRADC channels receives a private slot in the CTRL4
@@ -920,7 +920,7 @@ static int mxs_lradc_read_raw(struct iio_dev *iio_dev,
 
 		*val = lradc->vref_mv[chan->channel];
 		*val2 = chan->scan_type.realbits -
-			lradc->is_divided[chan->channel];
+			test_bit(chan->channel, &lradc->is_divided);
 		return IIO_VAL_FRACTIONAL_LOG2;
 
 	case IIO_CHAN_INFO_OFFSET:
@@ -965,14 +965,14 @@ static int mxs_lradc_write_raw(struct iio_dev *iio_dev,
 			/* divider by two disabled */
 			writel(1 << LRADC_CTRL2_DIVIDE_BY_TWO_OFFSET,
 			       lradc->base + LRADC_CTRL2 + STMP_OFFSET_REG_CLR);
-			lradc->is_divided[chan->channel] = 0;
+			clear_bit(chan->channel, &lradc->is_divided);
 			ret = 0;
 		} else if (val == scale_avail[MXS_LRADC_DIV_ENABLED].integer &&
 			   val2 == scale_avail[MXS_LRADC_DIV_ENABLED].nano) {
 			/* divider by two enabled */
 			writel(1 << LRADC_CTRL2_DIVIDE_BY_TWO_OFFSET,
 			       lradc->base + LRADC_CTRL2 + STMP_OFFSET_REG_SET);
-			lradc->is_divided[chan->channel] = 1;
+			set_bit(chan->channel, &lradc->is_divided);
 			ret = 0;
 		}