Documentation: devicetree: add Freescale SCC bindings

Add documentation for the Freescale Security Controller (SCC)
found on i.MX25 SoCs.
Signed-off-by: NSteffen Trumtrar <s.trumtrar@pengutronix.de>
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Documentation/devicetree/bindings/crypto/fsl-imx-scc.txt

+Freescale Security Controller (SCC)
+
+Required properties:
+- compatible : Should be "fsl,imx25-scc".
+- reg : Should contain register location and length.
+- interrupts : Should contain interrupt numbers for SCM IRQ and SMN IRQ.
+- interrupt-names : Should specify the names "scm" and "smn" for the
+		    SCM IRQ and SMN IRQ.
+- clocks: Should contain the clock driving the SCC core.
+- clock-names: Should be set to "ipg".
+
+Example:
+
+	scc: crypto@53fac000 {
+		compatible = "fsl,imx25-scc";
+		reg = <0x53fac000 0x4000>;
+		clocks = <&clks 111>;
+		clock-names = "ipg";
+		interrupts = <49>, <50>;
+		interrupt-names = "scm", "smn";
+	};