There is a option for that in "magic uv"Magic UV addon which is biuld inbundled with Blender. After enabling an addon, you should see "magic uv"Magic UV tab on the right side of the uv editorUV Editor window (press "n"N to show/hide entire toolbar).
Expand "Uv manipulation"UV Manipulation, enable "select tool"Select Tool, click on "flipped"Flipped.