x86: dts: Add device-tree labels for rtc and reset

Add labels for these nodes so that board DT files can reference them.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

arch/x86/dts/reset.dtsi

@@ -1,5 +1,5 @@
 / {
-	reset {
+	reset: reset {
 		compatible = "x86,reset";
 		u-boot,dm-pre-reloc;
 	};

arch/x86/dts/rtc.dtsi

@@ -1,5 +1,5 @@
 / {
-	rtc {
+	rtc: rtc {
 		compatible = "motorola,mc146818";
 		u-boot,dm-pre-reloc;
 		reg = <0x70 2>;