boards: m5stack: cores3: Add bus_5v fixed regulator

Add a `bus_5v` fixed-regulator node driven by the `BOOST_EN` pin. This
enables drivers and shields to reference the 5V supply through the standard
`vin-supply` property, providing correct power sequencing and runtime
control via Zephyr’s regulator API.

This regulator is equivalent to the `bus_5v` already defined on the M5Stack
Core2 board.

Signed-off-by: Chen Xingyu <hi@xingrz.me>

Author: xingrz

boards/m5stack/m5stack_cores3/Kconfig.defconfig

@@ -24,6 +24,11 @@ endif # LVGL
 
 # Takes good care of initialization priorities
 
+if REGULATOR_FIXED
+config REGULATOR_FIXED_INIT_PRIORITY
+	default 81
+endif
+
 if REGULATOR_AXP192_AXP2101
 config REGULATOR_AXP192_AXP2101_INIT_PRIORITY
 	default 81

boards/m5stack/m5stack_cores3/m5stack_cores3_procpu_common.dtsi

@@ -63,6 +63,12 @@
 			rotation = <0>;
 		};
 	};
+
+	bus_5v: bus_5v {
+		compatible = "regulator-fixed";
+		regulator-name = "bus_5v";
+		enable-gpios = <&aw9523b_gpio 15 GPIO_ACTIVE_HIGH>;
+	};
 };
 
 &usb_serial {