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/common/hush.c b/common/hush.c
index 8a74d22..4dd9513 100644
--- a/common/hush.c
+++ b/common/hush.c
@@ -1694,10 +1694,8 @@
 				}
 #endif
 				/* found - check max args */
-				if ((child->argc - i) > cmdtp->maxargs) {
-					cmd_usage(cmdtp);
-					return -1;
-				}
+				if ((child->argc - i) > cmdtp->maxargs)
+					return cmd_usage(cmdtp);
 #endif
 				child->argv+=i;  /* XXX horrible hack */
 #ifndef __U_BOOT__