[TF-M] memcpy variants

Just some minor observation:

There are various variants of memory functions in tfm core

* tfm_memory_utils.h defines a set of identical functions * tfm_core_utils.c/h has another set - functional equivalent with the C run-time library

Why are these functions duplicated? It would be Ok if they address some additional security concerns (that I currently don't understand). But todays implementation just add complexity.

Reinhard