dt-bindings: reset: imx7: update the compatible string

The i.MX7 SRC's compatible string should be "fsl,imx7d-src".
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/reset/fsl,imx7-src.txt

@@ -5,7 +5,7 @@ Please also refer to reset.txt in this directory for common reset
 controller binding usage.
 
 Required properties:
-- compatible: Should be "fsl,imx7-src", "syscon"
+- compatible: Should be "fsl,imx7d-src", "syscon"
 - reg: should be register base and length as documented in the
   datasheet
 - interrupts: Should contain SRC interrupt