arm64: dts: imx8mq-librem5-devkit: Mark buck2 as always on

Otherwise the A53 cores are shut down which doesn't end well.
Reported-by: David Heidelberg <david@ixit.cz>
Tested-by: David Heidelberg <david@ixit.cz>
Signed-off-by: Guido Günther <agx@sigxcpu.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mq-librem5-devkit.dts

@@ -324,6 +324,7 @@ buck2_reg: BUCK2 {
 				regulator-ramp-delay = <1250>;
 				rohm,dvs-run-voltage = <1000000>;
 				rohm,dvs-idle-voltage = <900000>;
+				regulator-always-on;
 			};
 
 			buck3_reg: BUCK3 {