platform/chrome: cros_ec_uart: fix race condition

serdev_device_set_client_ops() is called before `ec_dev` is fully
initialized.  This can result in cros_ec_uart_rx_bytes() being called
while `ec_dev` is still not initialized, resulting in a kernel panic.

Call serdev_device_set_client_ops() after `ec_dev` is initialized.

Fixes: 04a8bdd ("platform/chrome: cros_ec_uart: Add transport layer")
Signed-off-by: Robert Zieba <robertzieba@google.com>
[tzungbi: modified commit message and fixed context conflict.]
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Link: https://lore.kernel.org/r/20221229094738.2304044-1-tzungbi@kernel.org

drivers/platform/chrome/cros_ec_uart.c

@@ -270,7 +270,6 @@ static int cros_ec_uart_probe(struct serdev_device *serdev)
 	}
 
 	serdev_device_set_drvdata(serdev, ec_dev);
-	serdev_device_set_client_ops(serdev, &cros_ec_uart_client_ops);
 	init_waitqueue_head(&ec_uart->response.wait_queue);
 
 	ec_uart->serdev = serdev;
@@ -300,6 +299,8 @@ static int cros_ec_uart_probe(struct serdev_device *serdev)
 			   sizeof(struct ec_response_get_protocol_info);
 	ec_dev->dout_size = sizeof(struct ec_host_request);
 
+	serdev_device_set_client_ops(serdev, &cros_ec_uart_client_ops);
+
 	return cros_ec_register(ec_dev);
 }