arm64: dts: imx8mm-var-som: drop unused top-level compatible

The Variscite VAR-SOM-MX8MM System-on-Module cannot be used alone
without motherboard, so drop the top-level compatible field to avoid any
false impression that such usage is possible.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

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

@@ -8,7 +8,6 @@
 
 / {
 	model = "Variscite VAR-SOM-MX8MM module";
-	compatible = "variscite,var-som-mx8mm", "fsl,imx8mm";
 
 	chosen {
 		stdout-path = &uart4;