static-checks/common.sh: Use GERRIT_BRANCH param

Because static checks are used for both TF-A and TFTF repos. Thus, an
upsream job which calls static checks sets up GERRIT_BRANCH based on
the repo used, and we should use that.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I49c5207833129e15b632681ff25ed71830b7832e
1 file changed