Make ms-tpm-20-ref compile on Zephyr.

Zephyr by default adds these flags to all components which causes
unnecessary warnings in ms-tpm-20-ref.

WolfSSL pulls in Zephyr headers which cause conflicts with some macros
defined ms-tpm-ref. Eliminating Zephyr headers from WolfSSL is not
feasible due to extensive usage of Zephyr types in public types. Neither
this can be (easily) eliminated from ms-tpm-ref due to the same reason.
The approach used is the least invasive method.

Fix macro names conflicts and compiler warnings

We keep only those functions that are called by ms-tpm. Previously
Platform_fp.h had declarations for all "platform" functions but many of
them were used only internally. Keeping stuff private gives better
distinction between ms-tpm (universal) and platform specific
implementation.

Simulation mode introduces additional test code and assertions, some of
which are invalid in non-simulation.