staging/iio/mxs-lradc: fix preenable for multiple buffers

This fixes 'preenable failed: -EINVAL' error when using this driver.
Signed-off-by: NMichał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

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

@@ -690,7 +690,6 @@ static void mxs_lradc_trigger_remove(struct iio_dev *iio)
 static int mxs_lradc_buffer_preenable(struct iio_dev *iio)
 {
 	struct mxs_lradc *lradc = iio_priv(iio);
-	struct iio_buffer *buffer = iio->buffer;
 	int ret = 0, chan, ofs = 0;
 	unsigned long enable = 0;
 	uint32_t ctrl4_set = 0;
@@ -698,7 +697,7 @@ static int mxs_lradc_buffer_preenable(struct iio_dev *iio)
 	uint32_t ctrl1_irq = 0;
 	const uint32_t chan_value = LRADC_CH_ACCUMULATE |
 		((LRADC_DELAY_TIMER_LOOP - 1) << LRADC_CH_NUM_SAMPLES_OFFSET);
-	const int len = bitmap_weight(buffer->scan_mask, LRADC_MAX_TOTAL_CHANS);
+	const int len = bitmap_weight(iio->active_scan_mask, LRADC_MAX_TOTAL_CHANS);
 
 	if (!len)
 		return -EINVAL;
@@ -725,7 +724,7 @@ static int mxs_lradc_buffer_preenable(struct iio_dev *iio)
 		lradc->base + LRADC_CTRL1 + STMP_OFFSET_REG_CLR);
 	writel(0xff, lradc->base + LRADC_CTRL0 + STMP_OFFSET_REG_CLR);
 
-	for_each_set_bit(chan, buffer->scan_mask, LRADC_MAX_TOTAL_CHANS) {
+	for_each_set_bit(chan, iio->active_scan_mask, LRADC_MAX_TOTAL_CHANS) {
 		ctrl4_set |= chan << LRADC_CTRL4_LRADCSELECT_OFFSET(ofs);
 		ctrl4_clr |= LRADC_CTRL4_LRADCSELECT_MASK(ofs);
 		ctrl1_irq |= LRADC_CTRL1_LRADC_IRQ_EN(ofs);