arm/dts: add wdt node for omap3 and omap4

Add wdt node to support dt.

Signed-off-by: Xiao Jiang <[e-mail]>
Signed-off-by: Tony Lindgren <[e-mail]>

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

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

arch/arm/boot/dts/omap4.dtsi

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