windmove-wrap-around

windmove-wrap-around is a variable defined in `windmove.el'.
Its value is

nil

Documentation:
Whether movement off the edge of the frame wraps around.
If this variable is set to t, moving left from the leftmost window in
a frame will find the rightmost one, and similarly for the other
directions. The minibuffer is skipped over in up/down movements if it
is inactive.

You can customize this variable.