Add u-boot.dtsi specific to imx6-apalis with a watchdog enabled. If OP-TEE is loaded by SPL, it may use a watchdog to handle fails of u-boot running. Enable the watchdog in SPL to use it by OP-TEE. Signed-off-by: Ricardo Salveti <ricardo@foundries.io> Signed-off-by: Oleksandr Suvorov <oleksandr.suvorov@foundries.io> Reviewed-by: Igor Opaniuk <igor.opaniuk@foundries.io> Reviewed-by: Peng Fan <peng.fan@nxp.com>