Add secrets declaration to reusable workflow for GitHub App auth

Author: shreeya-patel98

.github/workflows/kernel-build-and-test-x86_64.yml

@@ -2,6 +2,11 @@ name: Automated kernel build and test (x86_64)
 
 on:
   workflow_call:
+    secrets:
+      APP_ID:
+        required: true
+      APP_PRIVATE_KEY:
+        required: true
 
 permissions:
   contents: read