github actions: Use reusable validate kernel commits workflow

Simplifies the workflow to use the reusable workflow defined in main
branch. This reduces duplication and makes the workflow easier to
maintain across multiple branches.

The workflow was renamed because it now includes validation over
and above just checking for upstream fixes

Author: bmastbergen

.github/workflows/upstream-commit-check.yml

@@ -0,0 +1,9 @@
+name: Validate Kernel Commits
+
+on:
+  pull_request:
+    types: [opened, synchronize, reopened]
+
+jobs:
+  check:
+    uses: ctrliq/kernel-src-tree/.github/workflows/validate-kernel-commits.yml@main