Use value_string for ctrl_type

Use value_string for enum ctrl_type instead of custom code. Add
corresponding unit tests.

Related: OS#1615
Change-Id: Icd4e96dd9f00876cb70b43cfcf42ab4f10311b28
diff --git a/tests/testsuite.at b/tests/testsuite.at
index a3be0e7..6d8c5d3 100644
--- a/tests/testsuite.at
+++ b/tests/testsuite.at
@@ -9,6 +9,12 @@
 AT_CHECK([$abs_top_builddir/tests/a5/a5_test], [0], [expout])
 AT_CLEANUP
 
+AT_SETUP([ctrl])
+AT_KEYWORDS([ctrl])
+cat $abs_srcdir/ctrl/ctrl_test.ok > expout
+AT_CHECK([$abs_top_builddir/tests/ctrl/ctrl_test], [0], [expout])
+AT_CLEANUP
+
 AT_SETUP([kasumi])
 AT_KEYWORDS([kasumi])
 cat $abs_srcdir/kasumi/kasumi_test.ok > expout