arm64: dts: imx8mq: add clock for SNVS RTC node

i.MX8MQ has clock gate for SNVS module, add clock info to SNVS
RTC node for clock management.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Leonard Crestez <leonard.crestez@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mq.dtsi

@@ -433,6 +433,8 @@ snvs_rtc: snvs-rtc-lp{
 					offset = <0x34>;
 					interrupts = <GIC_SPI 19 IRQ_TYPE_LEVEL_HIGH>,
 						<GIC_SPI 20 IRQ_TYPE_LEVEL_HIGH>;
+					clocks = <&clk IMX8MQ_CLK_SNVS_ROOT>;
+					clock-names = "snvs-rtc";
 				};
 
 			};