arm64: dts: imx8mm: Drop deprecated regulator-compatible from Variscite VAR-SOM-MX8MM

The "regulator-compatible" property is deprecated and unused, as the
match happens on the node name in Linux of_regulator_match() in case
the property is not present. Drop the deprecated property from DT.
Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mm-var-som.dtsi

@@ -231,7 +231,6 @@ ldo4_reg: LDO4 {
 			};
 
 			ldo5_reg: LDO5 {
-				regulator-compatible = "ldo5";
 				regulator-min-microvolt = <1800000>;
 				regulator-max-microvolt = <1800000>;
 				regulator-always-on;