arm64: dts: imx8mn: Add SNVS LPGPR

Add SNVS LPGPR bindings to MX8M Nano, the LPGPR is used to store
boot counter.

Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Marek Vasut <marex@nabladev.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

Author: Marek Vasut

arch/arm64/boot/dts/freescale/imx8mn.dtsi

@@ -628,6 +628,11 @@
 					wakeup-source;
 					status = "disabled";
 				};
+
+				snvs_lpgpr: snvs-lpgpr {
+					compatible = "fsl,imx8mn-snvs-lpgpr",
+						     "fsl,imx7d-snvs-lpgpr";
+				};
 			};
 
 			clk: clock-controller@30380000 {