add missing init file from origin SDK

buildroot-2021.05/board/cvitek/CV180X/overlay/mnt/system/S99msc
to
buildroot-2021.05/board/milkv/duo/overlay/mnt/system/S99msc

buildroot-2021.05/board/milkv/duo/overlay/mnt/system/S99msc

+#!/bin/sh
+
+case "$1" in
+  start)
+    printf "Starting msc: "
+    /etc/uhubon.sh device
+    /etc/run_usb.sh probe msc /dev/mmcblk0p1
+    /etc/run_usb.sh start
+    [ $? = 0 ] && echo "OK" || echo "FAIL"
+    ;;
+  stop)
+    printf "Stopping msc: "
+    echo "OK"
+    ;;
+  restart|reload)
+    "$0" stop
+    "$0" start
+    ;;
+  *)
+    echo "Usage: $0 {start|stop|restart}"
+    exit 1
+esac
+
+exit $?
+