DTO user API

[byrnedj]

This commit adds support for the DTO API. This public API allows the caller to pass an arbitrary function to execute while the DSA job is executing.

void dto_memcpy(void *dest, const void src, size_t n, int flags, callback_t cb, void args);

where callback_t cb is a function pointer in the calling application and flags pass various options to DSA.

We will add memcmp and memset, CRC32 and CRC with copy shortly once the framework is reviewed.