Standardize command usage messages with cmd_usage()

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
diff --git a/common/cmd_irq.c b/common/cmd_irq.c
index 04914c6..a47cde4 100644
--- a/common/cmd_irq.c
+++ b/common/cmd_irq.c
@@ -28,7 +28,7 @@
 {
 
 	if (argc != 2) {
-		printf ("Usage:\n%s\n", cmdtp->usage);
+		cmd_usage(cmdtp);
 		return 1;
 	}