ci: add call to check-config.sh

This is done to make sure the script is working correctly in different
environments (distro and kernel versions). In addition, we can see in
test logs which kernel features are enabled.

Note that I didn't want to have a separate job for GHA CI, so I just
added this to the end of shellcheck one.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

.github/workflows/validate.yml

@@ -118,6 +118,8 @@ jobs:
       - name: shellcheck
         run: |
           make shellcheck
+      - name: check-config.sh
+        run : ./script/check-config.sh
 
   deps:
     runs-on: ubuntu-20.04