asoc: wcd938x: Add default cases for port mapping

Return error in case of wrong path being selected
for port mapping and port params functions.

Change-Id: I5d66a9cd32e9c8e6d8ebac0ea073b1a1762407b6
Signed-off-by: Karthikeyan Mani <kmani@codeaurora.org>

asoc/codecs/wcd938x/wcd938x-slave.c

@@ -22,6 +22,11 @@ static int wcd938x_slave_bind(struct device *dev,
 	uint8_t devnum = 0;
 	struct swr_device *pdev = to_swr_device(dev);
 
+	if (!pdev) {
+		pr_err("%s: invalid swr device handle\n", __func__);
+		return -EINVAL;
+	}
+
 	ret = swr_get_logical_dev_num(pdev, pdev->addr, &devnum);
 	if (ret) {
 		dev_dbg(&pdev->dev,