Add unit tests for mm_radio.c

Add unit tests for mm_radio.c

- These tests use Google Mock to create mock objects and verify the behavior of the tested functions.
  The tests cover both positive and negative scenarios,
  including invalid input parameters and internal errors.
- With this addition, we significantly enhance the robustness and reliability of the mm-radio library,
  making it easier to maintain and extend over time.

[Version] 0.3.5
[Issue Type] Add unittest

Change-Id: Ie97ff03457ad0efde023156817156776672ad209