dm: test: replace dm_scan_dt() by of dm_extended_scan_fdt() in dm_do_test

This allows to scan the DT including all "clocks" node's sub-nodes
in which fixed-clock are defined.
All fixed-clock should be defined inside a clocks node which collect all
external oscillators. Until now, all clocks sub-nodes can't be binded except
if the "simple-bus" compatible string is added which is a hack.

Update test.dts by moving clk_fixed node inside clocks.

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>

arch/sandbox/dts/test.dts

@@ -127,10 +127,12 @@
 		compatible = "denx,u-boot-fdt-test";
 	};
 
-	clk_fixed: clk-fixed {
-		compatible = "fixed-clock";
-		#clock-cells = <0>;
-		clock-frequency = <1234>;
+	clocks {
+		clk_fixed: clk-fixed {
+			compatible = "fixed-clock";
+			#clock-cells = <0>;
+			clock-frequency = <1234>;
+		};
 	};
 
 	clk_sandbox: clk-sbox {

test/dm/test-main.c

@@ -92,7 +92,7 @@ static int dm_do_test(struct unit_test_state *uts, struct unit_test *test,
 	if (test->flags & DM_TESTF_PROBE_TEST)
 		ut_assertok(do_autoprobe(uts));
 	if (test->flags & DM_TESTF_SCAN_FDT)
-		ut_assertok(dm_scan_fdt(gd->fdt_blob, false));
+		ut_assertok(dm_extended_scan_fdt(gd->fdt_blob, false));
 
 	/*
 	 * Silence the console and rely on console reocrding to get