cmd_usage(): simplify return code handling

Lots of code use this construct:

	cmd_usage(cmdtp);
	return 1;

Change cmd_usage() let it return 1 - then we can replace all these
ocurrances by

	return cmd_usage(cmdtp);

This fixes a few places with incorrect return code handling, too.

Signed-off-by: Wolfgang Denk <wd@denx.de>
diff --git a/board/inka4x0/inkadiag.c b/board/inka4x0/inkadiag.c
index 637bb5a..cf82f61 100644
--- a/board/inka4x0/inkadiag.c
+++ b/board/inka4x0/inkadiag.c
@@ -168,8 +168,7 @@
 		printf("exit code: 0x%X\n", val);
 		return 0;
 	default:
-		cmd_usage(cmdtp);
-		break;
+		return cmd_usage(cmdtp);
 	}
 
 	return -1;
@@ -244,10 +243,8 @@
 	int combrd, baudrate, i, j, len;
 	int address;
 
-	if (argc < 5) {
-		cmd_usage(cmdtp);
-		return 1;
-	}
+	if (argc < 5)
+		return cmd_usage(cmdtp);
 
 	argc--;
 	argv++;
@@ -394,10 +391,8 @@
 	unsigned int period, freq;
 	int prev, i;
 
-	if (argc != 3) {
-		cmd_usage(cmdtp);
-		return 1;
-	}
+	if (argc != 3)
+		return cmd_usage(cmdtp);
 
 	argc--;
 	argv++;
@@ -474,8 +469,7 @@
 		return c->cmd(c, flag, argc, argv);
 	} else {
 		/* Unrecognized command */
-		cmd_usage(cmdtp);
-		return 1;
+		return cmd_usage(cmdtp);
 	}
 }