UT framework for mdio_bb driver fake mdio

[JoshuaJeyaraj]

Product: (OC-SDR, OC-LTE, OC-LTE, OC-Power, others)

Unit test

Component: (PSU, GBC, BBU, FEM, LED, ME)

GBC

Category: (Hardware, Software/stack, Firmware/bootloader, Documentation)

Software/stack

Describe the solution you'd like

Approach : Add infrastructure for accessing mdio registers .This infrastructure will be present in test/fake/*.c

Test Criteria : The Unity framework should be successful for all the planned testcases . The testcase list should be updated with the newly added testcases .