dt/bindings: Correct clk binding example for PIC32 DMT.

Update binding example based on new clock binding scheme.
[1] Documentation/devicetree/bindings/clock/microchip,pic32.txt
Signed-off-by: Purna Chandra Mandal <purna.mandal@microchip.com>
Acked-by: Rob Herring <robh@kernel.org>
Cc: Kumar Gala <galak@codeaurora.org>
Cc: Ian Campbell <ijc+devicetree@hellion.org.uk>
Cc: Joshua Henderson <digitalpeer@digitalpeer.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: devicetree@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13268/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Documentation/devicetree/bindings/watchdog/microchip,pic32-dmt.txt

@@ -8,12 +8,12 @@ Required properties:
 - compatible: must be "microchip,pic32mzda-dmt".
 - reg: physical base address of the controller and length of memory mapped
   region.
-- clocks: phandle of parent clock (should be &PBCLK7).
+- clocks: phandle of source clk. Should be <&rootclk PB7CLK>.
 
 Example:
 
 	watchdog@1f800a00 {
 		compatible = "microchip,pic32mzda-dmt";
 		reg = <0x1f800a00 0x80>;
-		clocks = <&PBCLK7>;
+		clocks = <&rootclk PB7CLK>;
 	};