Update check_files.py to accomodate non-standard license headers in TF-M config files

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/tests/scripts/check_files.py b/tests/scripts/check_files.py
index f6f6d6c..65fbc9f 100755
--- a/tests/scripts/check_files.py
+++ b/tests/scripts/check_files.py
@@ -373,8 +373,9 @@
         r'(ChangeLog|LICENSE|[-0-9A-Z_a-z]+\.md)\Z',
         # Files imported from TF-M, and not used except in test builds,
         # may be under a different license.
-        r'configs/crypto_config_profile_medium\.h\Z',
-        r'configs/tfm_mbedcrypto_config_profile_medium\.h\Z',
+        r'configs/ext/crypto_config_profile_medium\.h\Z',
+        r'configs/ext/tfm_mbedcrypto_config_profile_medium\.h\Z',
+        r'configs/ext/README\.md\Z',
         # Third-party file.
         r'dco\.txt\Z',
     ]