Standardize command usage messages with cmd_usage()

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
diff --git a/common/cmd_strings.c b/common/cmd_strings.c
index 7d05cf8..6f0cbca 100644
--- a/common/cmd_strings.c
+++ b/common/cmd_strings.c
@@ -15,7 +15,7 @@
 int do_strings(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
 {
 	if (argc == 1) {
-		printf("Usage:\n%s\n", cmdtp->usage);
+		cmd_usage(cmdtp);
 		return 1;
 	}