This reverts commit 427f8bc0.

When receiving an output update for the mode size we need to rotate the stored
width and height values if and only if we have an xdg-output for this output
since in this case the stored values describe the output's size in logical
space, i.e. rotated.

The here reverted commit made a code change with which we would not rotate though
when an xdg-output was available since in this case the need_rotate variable was
set to False what caused in the check afterwards the first branch to execute.