dt-bindings: crypto: Add binding for TI DTHE V2

Add DT binding for Texas Instruments DTHE V2 cryptography engine.

DTHE V2 is introduced as a part of TI AM62L SoC and can currently be
only found in it.

Signed-off-by: T Pratham <t-pratham@ti.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>