power: reset: st: Remove obsolete platforms from dt doc

This patch removes support for STiH415/6 SoC's from the
st-restart dt binding documentation, as support for these
platforms is being removed from the kernel. It also updates
the dt example to a currently supported platform.
Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Cc: <linux-pm@vger.kernel.org>
Signed-off-by: Sebastian Reichel <sre@kernel.org>

Documentation/devicetree/bindings/power/reset/st-reset.txt

 *Device-Tree bindings for ST SW reset functionality
 
 Required properties:
-- compatible: should be "st,<chip>-restart".
+- compatible: should be "stih407-restart".
 - st,syscfg: should be a phandle of the syscfg node.
 
 Example node:
 	restart {
-		compatible = "st,stih416-restart";
-		st,syscfg = <&syscfg_sbc>;
+		compatible = "st,stih407-restart";
+		st,syscfg = <&syscfg_sbc_reg>;
+		status = "okay";
 	};