cmd: misc: Fix return value for the sleep command

If sleeping has been interrupted, return CMD_RET_FAILURE instead of -1
(CMD_RET_USAGE).

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>

cmd/sleep.c

@@ -40,7 +40,7 @@ static int do_sleep(struct cmd_tbl *cmdtp, int flag, int argc,
 
 	while (get_timer(start) < delay) {
 		if (ctrlc())
-			return (-1);
+			return CMD_RET_FAILURE;
 
 		udelay(100);
 	}