arm64: dts: imx8mm-kontron-n801x-som: do not allow to switch off buck2

The buck2 output of the PMIC is the VDD core voltage of the cpu.
Switching off this will poweroff the CPU. Add the 'regulator-always-on'
property to avoid this.

Fixes: 8668d8b2 ("arm64: dts: Add the Kontron i.MX8M Mini SoMs and baseboards")
Signed-off-by: Heiko Thiery <heiko.thiery@gmail.com>
Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-som.dtsi

@@ -102,6 +102,7 @@ reg_vdd_arm: BUCK2 {
 				regulator-min-microvolt = <850000>;
 				regulator-max-microvolt = <950000>;
 				regulator-boot-on;
+				regulator-always-on;
 				regulator-ramp-delay = <3125>;
 				nxp,dvs-run-voltage = <950000>;
 				nxp,dvs-standby-voltage = <850000>;