Fix check signoff for github actions

Github actions checkout changed to pull only a single generated merge
commit instead of the actual PR commit id. This breaks check_format
test for signoff. Pulling history of 2 will include the actual commit
ID.

Change-Id: I7d83871159d24faaf2f8e6086f12173e14cbcf3c
Signed-off-by: Greg Tucker <greg.b.tucker@intel.com>

.github/workflows/ci.yml

@@ -13,6 +13,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2.3.4
+        with:
+          fetch-depth: 2
       - name: Install indent
         run: sudo apt install indent
       - name: Run format check