iio: adc: meson_saradc: Fix memory allocation order

meson_saradc's irq handler uses priv->regmap so make sure that it is
allocated before the irq get enabled.

This also fixes crash when CONFIG_DEBUG_SHIRQ is enabled, as device
managed resources are freed in the inverted order they had been
allocated, priv->regmap was freed before the spurious fake irq that
CONFIG_DEBUG_SHIRQ adds called the handler.

Fixes: 3af1091 ("iio: adc: meson-saradc: switch from polling to interrupt mode")
Reported-by: Elie Roudninski <xademax@gmail.com>
Signed-off-by: Remi Pommarel <repk@triplefau.lt>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Tested-by: Elie ROUDNINSKI <xademax@gmail.com>
Reviewed-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/meson_saradc.c

@@ -1219,6 +1219,11 @@ static int meson_sar_adc_probe(struct platform_device *pdev)
 	if (IS_ERR(base))
 		return PTR_ERR(base);
 
+	priv->regmap = devm_regmap_init_mmio(&pdev->dev, base,
+					     priv->param->regmap_config);
+	if (IS_ERR(priv->regmap))
+		return PTR_ERR(priv->regmap);
+
 	irq = irq_of_parse_and_map(pdev->dev.of_node, 0);
 	if (!irq)
 		return -EINVAL;
@@ -1228,11 +1233,6 @@ static int meson_sar_adc_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
-	priv->regmap = devm_regmap_init_mmio(&pdev->dev, base,
-					     priv->param->regmap_config);
-	if (IS_ERR(priv->regmap))
-		return PTR_ERR(priv->regmap);
-
 	priv->clkin = devm_clk_get(&pdev->dev, "clkin");
 	if (IS_ERR(priv->clkin)) {
 		dev_err(&pdev->dev, "failed to get clkin\n");