test: Update fdt_overlay to do init from tests

Rather than having an init function and then running the tests, create a
test-init function to do it. This will allow us to get rid of the
command function.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/test/fdt_overlay/cmd_ut_fdt_overlay.c b/test/fdt_overlay/cmd_ut_fdt_overlay.c
index ac8a3b2..c716c6b 100644
--- a/test/fdt_overlay/cmd_ut_fdt_overlay.c
+++ b/test/fdt_overlay/cmd_ut_fdt_overlay.c
@@ -81,6 +81,7 @@
 
 	return 0;
 }
+FDT_OVERLAY_TEST_INIT(fdt_overlay_init, 0);
 
 static int fdt_getprop_str(void *fdt, const char *path, const char *name,
 			   const char **out)
@@ -243,7 +244,6 @@
 	const int n_ents = UNIT_TEST_SUITE_COUNT(fdt_overlay);
 	int ret = -ENOMEM;
 
-	ut_assertok(fdt_overlay_init(uts));
 	ret = cmd_ut_category(uts, "fdt_overlay", "fdt_overlay_test_", tests,
 			      n_ents, argc, argv);