dt-bindings: amlogic: Add Internal Clock Measurer bindings

The Amlogic Meson SoCs embeds a clock measurer IP to measure the internal
clock paths frequencies.
Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>

Documentation/devicetree/bindings/soc/amlogic/clk-measure.txt

+Amlogic Internal Clock Measurer
+===============================
+
+The Amlogic SoCs contains an IP to measure the internal clocks.
+The precision is multiple of MHz, useful to debug the clock states.
+
+Required properties:
+- compatible: Shall contain one of the following :
+			"amlogic,meson-gx-clk-measure" for GX SoCs
+			"amlogic,meson8-clk-measure" for Meson8 SoCs
+			"amlogic,meson8b-clk-measure" for Meson8b SoCs
+- reg: base address and size of the Clock Measurer register space.
+
+Example:
+	clock-measure@8758 {
+		compatible = "amlogic,meson-gx-clk-measure";
+		reg = <0x0 0x8758 0x0 0x10>;
+	};