imx: Also clear powerdown enable bit for WDOG3 on i.MX6ULL

Clear powerdown enable bit for WDOG3 on i.MX6ULL to avoid unwanted
kernel reboots.

Suggested-by: Ye Li <ye.li@nxp.com>
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Stefano Babic <sbabic@denx.de>

arch/arm/mach-imx/init.c

@@ -78,7 +78,7 @@ void imx_set_wdog_powerdown(bool enable)
 	writew(enable, &wdog1->wmcr);
 	writew(enable, &wdog2->wmcr);
 
-	if (is_mx6sx() || is_mx6ul() || is_mx7())
+	if (is_mx6sx() || is_mx6ul() || is_mx6ull() || is_mx7())
 		writew(enable, &wdog3->wmcr);
 #ifdef CONFIG_MX7D
 	writew(enable, &wdog4->wmcr);