[nrf fromlist] boards: nrf: nRF54L20: Enable DCDC converter

Set the vregmain node to use the DCDC converter by default.

Upstream PR #: 90957

Signed-off-by: Adam Kondraciuk <[email protected]>

Author: adamkondraciuk

boards/nordic/nrf54l20pdk/nrf54l20_cpuapp_common.dtsi

@@ -37,6 +37,11 @@
 	load-capacitance-femtofarad = <15000>;
 };
 
+&vregmain {
+	status = "okay";
+	regulator-initial-mode = <NRF5X_REG_MODE_DCDC>;
+};
+
 &grtc {
 	owned-channels = <0 1 2 3 4 5 6 7 8 9 10 11>;
 	/* Channels 7-11 reserved for Zero Latency IRQs, 3-4 for FLPR */