busybox-initramfs: init: Allow overlay mount for mount types with parameters

This fixes overlay mount so it doesn't add $OVERLAY_DIR at the end of the
parameter list.
Kernel commandline parameter 'overlay' should now work for both NFS and
CIFS/SMB mounts, but alas, busybox CIFS mount doesn't (yet) support subdir
mounts (regular mount does). Leaving this in for posterity.

Signed-off-by: Alain Kalker <a.c.kalker@gmail.com>

packages/initramfs/sysutils/busybox-initramfs/scripts/init

@@ -249,7 +249,17 @@ NBD_DEVS="0"
       mkdir /storage/$OVERLAY_DIR
     fi
     /bin/busybox umount /storage
-    mount_part "$disk/$OVERLAY_DIR" "/storage" "rw,noatime"
+
+    # split $disk into $target,$options so we can append $OVERLAY_DIR
+      options="${disk#*,}"
+      target="${disk%%,*}"
+      if [ "$options" = "$disk" ]; then
+        disk="$target/$OVERLAY_DIR"
+      else
+        disk="$target/$OVERLAY_DIR,$options"
+      fi
+
+    mount_part "$disk" "/storage" "rw,noatime"
   }
 
   check_update() {