tools: Fetch more commits for commitlint to validate the commit

tools: Fetch more commits for commitlint to validate the commit

Note: It's necessary that you specify the fetch-depth argument to
actions/checkout@v2 step. By default they fetch only latest commit of the
branch, but we need more commits since we validate a range of commit messages.

Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>