crypto: atmel-aes - add support for Device Tree

Add support for Device Tree and use of the DMA DT API to
get the needed channels.
Documentation is added for these DT nodes.

Initial code by: Nicolas Royer and Eukrea.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>

Documentation/devicetree/bindings/crypto/atmel-crypto.txt

@@ -0,0 +1,23 @@
+* Atmel HW cryptographic accelerators
+
+These are the HW cryptographic accelerators found on some Atmel products.
+
+* Advanced Encryption Standard (AES)
+
+Required properties:
+- compatible : Should be "atmel,at91sam9g46-aes".
+- reg: Should contain AES registers location and length.
+- interrupts: Should contain the IRQ line for the AES.
+- dmas: List of two DMA specifiers as described in
+        atmel-dma.txt and dma.txt files.
+- dma-names: Contains one identifier string for each DMA specifier
+             in the dmas property.
+
+Example:
+aes@f8038000 {
+	compatible = "atmel,at91sam9g46-aes";
+	reg = <0xf8038000 0x100>;
+	interrupts = <43 4 0>;
+	dmas = <&dma1 2 18>,
+	       <&dma1 2 19>;
+	dma-names = "tx", "rx";