NXP: MLK-11476 iio: adc: Enable i.MX6SX adc driver.

Enable i.MX6SX adc driver. ADC driver will try getting ADC controller
channel number via device tree, because i.MX chip enable 4 channels
on each controller.

Signed-off-by: Luwei Zhou <b45643@freescale.com>
Signed-off-by: Fugang Duan <B38611@freescale.com>
(cherry picked from commit 9a1c0b13424b1c8f2cddbe863cdcdc04ecd6a822)

Using this patch to provide a number of channel limitation if the
supported channel number is smaller than the maximum channel number.

Signed-off-by: Stefan Riedmueller <s.riedmueller@phytec.de>
Signed-off-by: Christoph Fritz <chf@fritzc.com>
Signed-off-by: Christian Hemp <c.hemp@phytec.de>
Signed-off-by: Jan Remmet <j.remmet@phytec.de>
Signed-off-by: Yunus Bas <y.bas@phytec.de>
Signed-off-by: Andrej Picej <andrej.picej@norik.com>
Reviewed-by: Yunus Bas <y.bas@phytec.de>

drivers/iio/adc/vf610_adc.c

@@ -803,6 +803,7 @@ static int vf610_adc_probe(struct platform_device *pdev)
  struct iio_dev *indio_dev;
  int irq;
  int ret;
+ u32 channels;
 
  indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(struct vf610_adc));
  if (!indio_dev) {
@@ -858,11 +859,16 @@ static int vf610_adc_probe(struct platform_device *pdev)
 
  init_completion(&info->completion);
 
+ ret = of_property_read_u32(pdev->dev.of_node,
+ "num-channels", &channels);
+ if (ret)
+ channels = ARRAY_SIZE(vf610_adc_iio_channels);
+
  indio_dev->name = dev_name(&pdev->dev);
  indio_dev->info = &vf610_adc_iio_info;
  indio_dev->modes = INDIO_DIRECT_MODE;
  indio_dev->channels = vf610_adc_iio_channels;
- indio_dev->num_channels = ARRAY_SIZE(vf610_adc_iio_channels);
+ indio_dev->num_channels = (int)channels;
 
  ret = clk_prepare_enable(info->clk);
  if (ret) {