dt-bindings: crypto: Add TI SA2UL crypto accelerator documentation

The Security Accelerator Ultra Lite (SA2UL) subsystem provides hardware
cryptographic acceleration for the following use cases:

* Encryption and authentication for secure boot
* Encryption and authentication of content in applications
  requiring DRM (digital rights management) and
  content/asset protection

SA2UL provides support for number of different cryptographic algorithms
including SHA1, SHA256, SHA512, AES, 3DES, and various combinations of
the previous for AEAD use.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Keerthy <j-keerthy@ti.com>
[t-kristo@ti.com: converted documentation to yaml]
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>