tests: add LTP in the default tests

Signed-off-by: Fathi Boudra <fathi.boudra@linaro.org>
diff --git a/lava-submit.py b/lava-submit.py
index 9f000a3..b05bbf7 100755
--- a/lava-submit.py
+++ b/lava-submit.py
@@ -34,6 +34,7 @@
 tests_nano = [
     'device-tree',
     'gatortests',
+    'ltp',
     'perf',
     'pwrmgmt',
     'smoke-tests-basic',