ARM: dts: rskrza1: set rtc_x1 clock value

Enable the 32.768 kHz RTC_X1 clock by setting the frequency value to
non-zero.
Signed-off-by: NChris Brandt <chris.brandt@renesas.com>
Reviewed-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NSimon Horman <horms+renesas@verge.net.au>

arch/arm/boot/dts/r7s72100-rskrza1.dts

@@ -43,6 +43,10 @@
 	clock-frequency = <48000000>;
 };
 
+&rtc_x1_clk {
+	clock-frequency = <32768>;
+};
+
 &mtu2 {
 	status = "okay";
 };