CI: Add a check for pre-schema driver model tags

These should not be used anymore. Add a check to ensure they don't creek
back into U-Boot. Use bootph-... instead.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/.azure-pipelines.yml b/.azure-pipelines.yml
index 947c400..8327edf 100644
--- a/.azure-pipelines.yml
+++ b/.azure-pipelines.yml
@@ -213,6 +213,18 @@
           export PYTHONPATH=${UBOOT_TRAVIS_BUILD_DIR}/scripts/dtc/pylibfdt
           make pylint_err
 
+  - job: check_for_pre_schema_tags
+    displayName: 'Check for pre-schema driver model tags'
+    pool:
+      vmImage: $(ubuntu_vm)
+    container:
+      image: $(ci_runner_image)
+      options: $(container_option)
+    steps:
+      # If grep succeeds and finds a match the test fails as we should
+      # have no matches.
+      - script: git grep u-boot,dm- -- '*.dts*' && exit 1 || exit 0
+
 - stage: test_py
   jobs:
   - job: test_py