tests: benchmark: timing_info: Change API/variable Name.

The API/Variable names in timing_info looks very speicific to
platform (like systick etc), whereas these variabled are used
across platforms (nrf/arm/quark).
So this patch :-
1. changing API/Variable names to generic one.
2. Creating some of Macros whose implimentation is platform
depenent.

Jira: ZEP-2314

Signed-off-by: Youvedeep Singh <youvedeep.singh@intel.com>