arm64: dts: imx8mm-kontron: Add RTC aliases

Add aliases for the RTCs on the board and on the SoC. This ensures that
the primary RTC is always the one on the board that has a buffered supply
and maximum accuracy.

This is a direct port of the pending commit from linux-next.

Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>
Reviewed-by: Fabio Estevam <festevam@denx.de>
diff --git a/arch/arm/dts/imx8mm-kontron-bl.dts b/arch/arm/dts/imx8mm-kontron-bl.dts
index a079322..dcec57c 100644
--- a/arch/arm/dts/imx8mm-kontron-bl.dts
+++ b/arch/arm/dts/imx8mm-kontron-bl.dts
@@ -13,6 +13,8 @@
 
 	aliases {
 		ethernet1 = &usbnet;
+		rtc0 = &rx8900;
+		rtc1 = &snvs_rtc;
 	};
 
 	/* fixed crystal dedicated to mcp2515 */
@@ -136,7 +138,7 @@
 	pinctrl-0 = <&pinctrl_i2c4>;
 	status = "okay";
 
-	rtc@32 {
+	rx8900: rtc@32 {
 		compatible = "epson,rx8900";
 		reg = <0x32>;
 	};