ASoC: rockchip: i2s: Fix NULL pointer dereference when pinctrl is not found

Commit a5450aba ("ASoC: rockchip: i2s: switch BCLK to GPIO") switched
BCLK to GPIO functions when probing the i2s bus interface, but missed
adding a check for when devm_pinctrl_get() returns an error.  This can lead
to the following NULL pointer dereference on a rockpro64-v2 if there are no
"pinctrl" properties in the i2s device tree node.

Check that i2s->pinctrl is valid before attempting to search for the
bclk_on and bclk_off pinctrl states.

Fixes: a5450aba ("ASoC: rockchip: i2s: switch BCLK to GPIO")
Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Link: https://lore.kernel.org/r/20220711130522.401551-1-alexandru.elisei@arm.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/rockchip/rockchip_i2s.c

@@ -808,8 +808,11 @@ static int rockchip_i2s_probe(struct platform_device *pdev)
 
 	i2s->bclk_ratio = 64;
 	i2s->pinctrl = devm_pinctrl_get(&pdev->dev);
-	if (IS_ERR(i2s->pinctrl))
+	if (IS_ERR(i2s->pinctrl)) {
 		dev_err(&pdev->dev, "failed to find i2s pinctrl\n");
+		ret = PTR_ERR(i2s->pinctrl);
+		goto err_clk;
+	}
 
 	i2s->bclk_on = pinctrl_lookup_state(i2s->pinctrl,
 				   "bclk_on");