video: Begin support for measuring multiple lines of text

Update the vidconsole API so that measure() can measure multiple lines
of text. This will make it easier to implement multi-line fields in
expo.

Tidy up the function comments while we are here.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/video/vidconsole-uclass.c b/drivers/video/vidconsole-uclass.c
index a1dfd35..4ca41dc 100644
--- a/drivers/video/vidconsole-uclass.c
+++ b/drivers/video/vidconsole-uclass.c
@@ -608,14 +608,17 @@
 }
 
 int vidconsole_measure(struct udevice *dev, const char *name, uint size,
-		       const char *text, struct vidconsole_bbox *bbox)
+		       const char *text, struct vidconsole_bbox *bbox,
+		       struct alist *lines)
 {
 	struct vidconsole_priv *priv = dev_get_uclass_priv(dev);
 	struct vidconsole_ops *ops = vidconsole_get_ops(dev);
 	int ret;
 
 	if (ops->measure) {
-		ret = ops->measure(dev, name, size, text, bbox);
+		if (lines)
+			alist_empty(lines);
+		ret = ops->measure(dev, name, size, text, bbox, lines);
 		if (ret != -ENOSYS)
 			return ret;
 	}