rpmsg: virtio: Fix possible double free in rpmsg_virtio_add_ctrl_dev()

vch will be free in virtio_rpmsg_release_device() when
rpmsg_ctrldev_register_device() fails. There is no need to call
kfree() again.

Fixes: c486682a ("rpmsg: virtio: Register the rpmsg_char device")
Signed-off-by: Hangyu Hua <hbh25y@gmail.com>
Tested-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
Link: https://lore.kernel.org/r/20220426060536.15594-3-hbh25y@gmail.comSigned-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

drivers/rpmsg/virtio_rpmsg_bus.c

@@ -851,7 +851,7 @@ static struct rpmsg_device *rpmsg_virtio_add_ctrl_dev(struct virtio_device *vdev
 
 	err = rpmsg_ctrldev_register_device(rpdev_ctrl);
 	if (err) {
-		kfree(vch);
+		/* vch will be free in virtio_rpmsg_release_device() */
 		return ERR_PTR(err);
 	}