arm/dts: add wdt node for omap3 and omap4

Add wdt node to support dt.
Signed-off-by: NXiao Jiang <jgq516@gmail.com>
Signed-off-by: NTony Lindgren <tony@atomide.com>

Documentation/devicetree/bindings/watchdog/omap-wdt.txt

+TI Watchdog Timer (WDT) Controller for OMAP
+
+Required properties:
+compatible:
+- "ti,omap3-wdt" for OMAP3
+- "ti,omap4-wdt" for OMAP4
+- ti,hwmods: Name of the hwmod associated to the WDT
+
+Examples:
+
+wdt2: wdt@4a314000 {
+	compatible = "ti,omap4-wdt", "ti,omap3-wdt";
+	ti,hwmods = "wd_timer2";
+};

arch/arm/boot/dts/omap3.dtsi

@@ -215,5 +215,10 @@
 			compatible = "ti,omap3-hsmmc";
 			ti,hwmods = "mmc3";
 		};
+
+		wdt2: wdt@48314000 {
+			compatible = "ti,omap3-wdt";
+			ti,hwmods = "wd_timer2";
+		};
 	};
 };

arch/arm/boot/dts/omap4.dtsi

@@ -272,5 +272,10 @@
 			ti,hwmods = "mmc5";
 			ti,needs-special-reset;
 		};
+
+		wdt2: wdt@4a314000 {
+			compatible = "ti,omap4-wdt", "ti,omap3-wdt";
+			ti,hwmods = "wd_timer2";
+		};
 	};
 };