watchdog: aspeed: restore default value of reset_mask

This is required for the current Linux kernel to reboot. It should also
probably be fixed in Linux.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Simon Glass <sjg@chromium.org>

drivers/watchdog/ast_wdt.c

@@ -50,6 +50,7 @@ static int ast_wdt_stop(struct udevice *dev)
 
 	clrbits_le32(&priv->regs->ctrl, WDT_CTRL_EN);
 
+	writel(WDT_RESET_DEFAULT, &priv->regs->reset_mask);
 	return 0;
 }