check-names: Consider crypto-sourced header files

Many identifiers come from Mbed Crypto. Teach check-names.sh to look in
the crypto submodule for identifiers, to avoid incorrect test results.
diff --git a/tests/scripts/list-identifiers.sh b/tests/scripts/list-identifiers.sh
index cc9c54f..0d63284 100755
--- a/tests/scripts/list-identifiers.sh
+++ b/tests/scripts/list-identifiers.sh
@@ -32,9 +32,9 @@
 
 if [ $INTERNAL ]
 then
-    HEADERS=$( ls include/mbedtls/*_internal.h | egrep -v 'compat-1\.3\.h|bn_mul' )
+    HEADERS=$( ls include/mbedtls/*_internal.h crypto/include/mbedtls/*_internal.h | egrep -v 'compat-1\.3\.h|bn_mul' )
 else
-    HEADERS=$( ls include/mbedtls/*.h | egrep -v 'compat-1\.3\.h|bn_mul' )
+    HEADERS=$( ls include/mbedtls/*.h crypto/include/mbedtls/*.h | egrep -v 'compat-1\.3\.h|bn_mul' )
 fi
 
 rm -f identifiers