ARM: mvebu: Add Core Divider clock device-tree binding

The Armada 370/XP SoCs have a Core Divider clock providing
several clocks. For now, only the NAND clock is supported.
Reviewed-by: NGregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: NEzequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: NJason Cooper <jason@lakedaemon.net>

Documentation/devicetree/bindings/clock/mvebu-corediv-clock.txt

+* Core Divider Clock bindings for Marvell MVEBU SoCs
+
+The following is a list of provided IDs and clock names on Armada 370/XP:
+ 0 = nand (NAND clock)
+
+Required properties:
+- compatible : must be "marvell,armada-370-corediv-clock"
+- reg : must be the register address of Core Divider control register
+- #clock-cells : from common clock binding; shall be set to 1
+- clocks : must be set to the parent's phandle
+
+Example:
+
+corediv_clk: corediv-clocks@18740 {
+	compatible = "marvell,armada-370-corediv-clock";
+	reg = <0x18740 0xc>;
+	#clock-cells = <1>;
+	clocks = <&pll>;
+};