dtc: Mark various internal functions static

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
diff --git a/scripts/dtc/data.c b/scripts/dtc/data.c
index dd2e3d3..fe555e8 100644
--- a/scripts/dtc/data.c
+++ b/scripts/dtc/data.c
@@ -217,7 +217,7 @@
 	return d;
 }
 
-struct data data_append_markers(struct data d, struct marker *m)
+static struct data data_append_markers(struct data d, struct marker *m)
 {
 	struct marker **mp = &d.markers;