code-coverage: bugfix landing page and add comments

- Fix in conditional where a true merge status enables generating
code coverage summary at landing page in tf-a-ci-gateway job.
- Add/modify code comments/function names where occurs
the generation of code coverage merge reports.

Signed-off-by: Saul Romero <saul.romero@arm.com>
Change-Id: I1d3f9e33268c3b5a002f985d9f4fe59f8c588a83
1 file changed