xwayland: Set rotated mode with xdg-output

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 prior code did 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.

In order to remove the double negation this variable implied it gets replaced
with a simple check on the xdg-output directly.

Signed-off-by: Roman Gilg <subdiff@gmail.com>
4 jobs for xwl-output in 4 minutes and 39 seconds (queued for 1 second)