test: Allow SPL to run any available test

At present SPL only runs driver model tests. Update it to run all
available tests, i.e. in any test suite.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/test/dm/test-dm.c b/test/dm/test-dm.c
index 729becf..9ba2ba2 100644
--- a/test/dm/test-dm.c
+++ b/test/dm/test-dm.c
@@ -20,7 +20,16 @@
 
 DECLARE_GLOBAL_DATA_PTR;
 
-int dm_test_run(const char *test_name)
+/**
+ * dm_test_run() - Run driver model tests
+ *
+ * Run all the available driver model tests, or a selection
+ *
+ * @test_name: Name of single test to run (e.g. "dm_test_fdt_pre_reloc" or just
+ *	"fdt_pre_reloc"), or NULL to run all
+ * @return 0 if all tests passed, 1 if not
+ */
+static int dm_test_run(const char *test_name)
 {
 	struct unit_test *tests = UNIT_TEST_SUITE_START(dm_test);
 	const int n_ents = UNIT_TEST_SUITE_COUNT(dm_test);