tf-a-tftf-gerrit-tforg-l2: Add TF_GERRIT_BRANCH, TF_GERRIT_REFSPEC params

For consistency across jobs, to support building with different branches
(mainline/LTS).

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I3995d9e11d9c004794279e33162820c57e4b7822
1 file changed