Documentation: crypto: Add DT binding info for the img hw hash accelerator

This adds the binding documentation for the Imagination Technologies hash
accelerator that provides hardware acceleration for SHA1/SHA224/SHA256/MD5
hashes.  This hardware will be present in the upcoming pistachio SoC.
Signed-off-by: James Hartley <james.hartley@imgtec.com>
Reviewed-by: Andrew Bresticker <abrestic@chromium.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Documentation/devicetree/bindings/crypto/img-hash.txt

+Imagination Technologies hardware hash accelerator
+
+The hash accelerator provides hardware hashing acceleration for
+SHA1, SHA224, SHA256 and MD5 hashes
+
+Required properties:
+
+- compatible : "img,hash-accelerator"
+- reg : Offset and length of the register set for the module, and the DMA port
+- interrupts : The designated IRQ line for the hashing module.
+- dmas : DMA specifier as per Documentation/devicetree/bindings/dma/dma.txt
+- dma-names : Should be "tx"
+- clocks : Clock specifiers
+- clock-names : "sys" Used to clock the hash block registers
+		"hash" Used to clock data through the accelerator
+
+Example:
+
+	hash: hash@18149600 {
+	compatible = "img,hash-accelerator";
+		reg = <0x18149600 0x100>, <0x18101100 0x4>;
+		interrupts = <GIC_SHARED 59 IRQ_TYPE_LEVEL_HIGH>;
+		dmas = <&dma 8 0xffffffff 0>;
+		dma-names = "tx";
+		clocks = <&cr_periph SYS_CLK_HASH>, <&clk_periph PERIPH_CLK_ROM>;
+		clock-names = "sys", "hash";
+	};