gateway: working shell on uart0 and mcumgr on usb_serial, minimal OS mgmt config\n

Signed-off-by: Eduard Iten <eduard@iten.pro>

software/apps/gateway/sysbuild/mcuboot.overlay

@@ -0,0 +1,12 @@
+#include "../boards/common_4MB.dtsi"
+
+/* MCUboot Configuration - Bootloader goes to boot_partition (0x0) */
+/ {
+    chosen {
+        zephyr,code-partition = &boot_partition;
+    };
+    aliases {
+        mcuboot-button0 = &user_button1;
+    };
+    
+};