DM: WDT: Convert WDT driver to use DM/DTS (including SYSRESET)

This commit enables support for CONFIG_WDT in the U-Boot proper. Moreover,
the SYSRESET_WATCHDOG driver is used to support 'reset' command.

As SPL is not yet ready for DM conversion, the CONFIG_HW_WATCHDOG is
enabled for it. This allows the legacy SPL code to work properly.

Signed-off-by: Lukasz Majewski <lukma@denx.de>
diff --git a/arch/arm/dts/imx6q-display5-u-boot.dtsi b/arch/arm/dts/imx6q-display5-u-boot.dtsi
index b942218..aa660b5 100644
--- a/arch/arm/dts/imx6q-display5-u-boot.dtsi
+++ b/arch/arm/dts/imx6q-display5-u-boot.dtsi
@@ -31,6 +31,11 @@
 	chosen {
 		stdout-path = &uart5;
 	};
+
+	wdt-reboot {
+		compatible = "wdt-reboot";
+		wdt = <&wdog1>;
+	};
 };
 
 &i2c3 {