gitlab-ci: Extract OpenSBI job rules to reusable section

gitlab-ci: Extract OpenSBI job rules to reusable section

All jobs depending on 'docker-opensbi' job must use at most all
the rules that triggers it. The simplest way to ensure that
is to always use the same rules. Extract all the rules to a
reusable section, and include this section (with the 'extends'
keyword) in both 'docker-opensbi' and 'build-opensbi' jobs.

The problem was introduced in commit c6fc0fc1a71 ("gitlab-ci.yml:
Add jobs to build OpenSBI firmware binaries"), but was revealed in
commit 91e9c47e50a ("docker: OpenSBI build job depends on OpenSBI
container").

This fix is similar to the one used with the EDK2 firmware job in
commit ac0595cf6b3 ("gitlab-ci: Extract EDK2 job rules to reusable
section").

Reported-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Willian Rampazzo <willianr@redhat.com>
Message-Id: <20210720164829.3949558-1-philmd@redhat.com>
Message-Id: <20210720232703.10650-30-alex.bennee@linaro.org>