video: Mark truetype_measure() static

This function is not used outside this file, so mark it static.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/video/console_truetype.c b/drivers/video/console_truetype.c
index 242b8b7..14fb81e 100644
--- a/drivers/video/console_truetype.c
+++ b/drivers/video/console_truetype.c
@@ -718,8 +718,8 @@
 	return 0;
 }
 
-int truetype_measure(struct udevice *dev, const char *name, uint size,
-		     const char *text, struct vidconsole_bbox *bbox)
+static int truetype_measure(struct udevice *dev, const char *name, uint size,
+			    const char *text, struct vidconsole_bbox *bbox)
 {
 	struct console_tt_metrics *met;
 	stbtt_fontinfo *font;