several changes on fvp yaml generation

The CR-01, starting at [1], has been fully tested and it uncovered
several issues on the fvp yaml generation code section which this
commit addresses.

[1] https://review.trustedfirmware.org/c/ci/tf-a-job-configs/+/6217

Signed-off-by: Leonardo Sandoval <leonardo.sandoval@linaro.org>
Change-Id: I46af7eeeee7cff8434bfb417527e8e8c32a09ab9
3 files changed