ARM: dts: imx6qdl: Assign corresponding clocks instead of dummy clock

i.MX6Q/DL's WDOGs use IMX6QDL_CLK_IPG as clock root, assign
IMX6QDL_CLK_IPG to them instead of IMX6QDL_CLK_DUMMY.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx6qdl.dtsi

@@ -675,14 +675,14 @@ wdog1: wdog@20bc000 {
 				compatible = "fsl,imx6q-wdt", "fsl,imx21-wdt";
 				reg = <0x020bc000 0x4000>;
 				interrupts = <0 80 IRQ_TYPE_LEVEL_HIGH>;
-				clocks = <&clks IMX6QDL_CLK_DUMMY>;
+				clocks = <&clks IMX6QDL_CLK_IPG>;
 			};
 
 			wdog2: wdog@20c0000 {
 				compatible = "fsl,imx6q-wdt", "fsl,imx21-wdt";
 				reg = <0x020c0000 0x4000>;
 				interrupts = <0 81 IRQ_TYPE_LEVEL_HIGH>;
-				clocks = <&clks IMX6QDL_CLK_DUMMY>;
+				clocks = <&clks IMX6QDL_CLK_IPG>;
 				status = "disabled";
 			};