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 <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Cc: Kumar Gala <[e-mail]>
Cc: Ian Campbell <[e-mail]>
Cc: Joshua Henderson <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Patchwork: https://patchwork.linux-mips.org/patch/13268/
Signed-off-by: Ralf Baechle <[e-mail]>

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

···
 - 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>;
 	};