Bluetooth: hci_qca: Fix an error pointer dereference

When a function like devm_clk_get_optional() function returns both error
pointers on error and NULL then the NULL return means that the optional
feature is deliberately disabled.  It is a special sort of success and
should not trigger an error message.  The surrounding code should be
written to check for NULL and not crash.

On the other hand, if we encounter an error, then the probe from should
clean up and return a failure.

In this code, if devm_clk_get_optional() returns an error pointer then
the kernel will crash inside the call to:

	clk_set_rate(qcadev->susclk, SUSCLK_RATE_32KHZ);

The error handling must be updated to prevent that.

Fixes: 77131dfe ("Bluetooth: hci_qca: Replace devm_gpiod_get() with devm_gpiod_get_optional()")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

drivers/bluetooth/hci_qca.c

@@ -1962,17 +1962,17 @@ static int qca_serdev_probe(struct serdev_device *serdev)
 		}
 
 		qcadev->susclk = devm_clk_get_optional(&serdev->dev, NULL);
-		if (!qcadev->susclk) {
+		if (IS_ERR(qcadev->susclk)) {
 			dev_warn(&serdev->dev, "failed to acquire clk\n");
-		} else {
-			err = clk_set_rate(qcadev->susclk, SUSCLK_RATE_32KHZ);
-			if (err)
-				return err;
-
-			err = clk_prepare_enable(qcadev->susclk);
-			if (err)
-				return err;
+			return PTR_ERR(qcadev->susclk);
 		}
+		err = clk_set_rate(qcadev->susclk, SUSCLK_RATE_32KHZ);
+		if (err)
+			return err;
+
+		err = clk_prepare_enable(qcadev->susclk);
+		if (err)
+			return err;
 
 		err = hci_uart_register_device(&qcadev->serdev_hu, &qca_proto);
 		if (err) {