imx53-qsb: Convert to watchdog driver model

Commit 68dcbdd5 ("ARM: imx: Add weak default reset_cpu()") caused
the 'reset' command in U-Boot to not cause a board reset.

Fix it by switching to the watchdog driver model via sysreset, which
is the preferred method for implementing the watchdog reset.

Signed-off-by: Fabio Estevam <festevam@gmail.com>

arch/arm/dts/imx53-qsb-u-boot.dtsi

+// SPDX-License-Identifier: GPL-2.0+
+
+/ {
+	wdt-reboot {
+		compatible = "wdt-reboot";
+		wdt = <&wdog1>;
+		bootph-pre-ram;
+	};
+};
+
+&wdog1 {
+	bootph-pre-ram;
+};

configs/mx53loco_defconfig

@@ -60,6 +60,8 @@ CONFIG_POWER_FSL=y
 CONFIG_POWER_I2C=y
 CONFIG_DM_SERIAL=y
 CONFIG_MXC_UART=y
+CONFIG_SYSRESET=y
+CONFIG_SYSRESET_WATCHDOG=y
 CONFIG_USB=y
 CONFIG_USB_EHCI_MX5=y
 CONFIG_USB_STORAGE=y
@@ -67,3 +69,4 @@ CONFIG_USB_HOST_ETHER=y
 CONFIG_USB_ETHER_ASIX=y
 CONFIG_USB_ETHER_MCS7830=y
 CONFIG_USB_ETHER_SMSC95XX=y
+CONFIG_IMX_WATCHDOG=y