Hi,
Assuming you are using the windows PC.
Do not insert the Linux image and connect Galileo to PC.
Remove the Linux image and then connect the Galileo. You should see Gadget Serial v2.4
Locate the Gadget Serial v2.4 device, under the Other devices tree. Right-click that and select Update Driver Software
Then follow the steps mentioned here:
https://communities.intel.com/docs/DOC-22872#jive_content_id_Step_3__Install_DriversBack_to_Top