rpmsg: virtio: fix compilation warning for virtio_rpmsg_channel description

Complete the virtio_rpmsg_channel structure description to fix a
compilation warning with W=1 option:

drivers/rpmsg/virtio_rpmsg_bus.c:95: warning: Cannot understand
 * @vrp: the remote processor this channel belongs to
Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Link: https://lore.kernel.org/r/20200731074850.3262-1-arnaud.pouliquen@st.comSigned-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/rpmsg/virtio_rpmsg_bus.c

@@ -123,7 +123,12 @@ enum rpmsg_ns_flags {
 };
 
 /**
- * @vrp: the remote processor this channel belongs to
+ * struct virtio_rpmsg_channel - rpmsg channel descriptor
+ * @rpdev: the rpmsg channel device
+ * @vrp: the virtio remote processor device this channel belongs to
+ *
+ * This structure stores the channel that links the rpmsg device to the virtio
+ * remote processor device.
  */
 struct virtio_rpmsg_channel {
 	struct rpmsg_device rpdev;