tinycrypt: Add test case for the CTR PRNG algorithm

This commit adds the test case for the CTR PRNG algorithm.

Origin: https://github.com/01org/tinycrypt/tree/v0.2.0

The code was refactored to eliminate malloc and free function
calls and checkpatch errors. However, many warnings are still
present. Refactoring history is available at:

Repo:	https://gitlab.com/santes/tinycrypt/commits/refactoring


Commit:	5d0482c26c4ad69e7854dde58d15bb57a3e5f18f

Jira: ZEP-614
Jira: ZEP-860

Change-Id: I0620868d092941931762718c81fe13fc01f251b2
Signed-off-by: Flavio Santes <flavio.santes@intel.com>