sandbox: Correct help message <arg> garbling

The <arg> is displayed for options with no argument, and omitted for those
with an argument. Swap this around.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>

arch/sandbox/cpu/start.c

@@ -50,9 +50,9 @@ int sandbox_early_getopt_check(void)
 
 		/* then the long flag */
 		if (opt->has_arg)
-			printf("--%-*s", max_noarg_len, opt->flag);
-		else
 			printf("--%-*s <arg> ", max_arg_len, opt->flag);
+		else
+			printf("--%-*s", max_noarg_len, opt->flag);
 
 		/* finally the help text */
 		printf("  %s\n", opt->help);