watchdog: tangier: Convert to use WDT class

Convert legacy driver to use watchdog class.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/arch/x86/dts/edison.dts b/arch/x86/dts/edison.dts
index e8564bb..c048765 100644
--- a/arch/x86/dts/edison.dts
+++ b/arch/x86/dts/edison.dts
@@ -104,6 +104,10 @@
 		reg = <0xff009000 0x1000>;
 	};
 
+	watchdog: wdt@0 {
+		compatible = "intel,tangier-wdt";
+	};
+
 	reset {
 		compatible = "intel,reset-tangier";
 		u-boot,dm-pre-reloc;