xwayland: rotate logical size for RRMode

The logical size is the size of the output in the global compositor
space. The mode width/height should be scaled as in the logical
size, but shouldn't be transformed. Thus we need to rotate back
the logical size to be able to use it as the mode width/height.

This fixes issues with pointer input on transformed outputs.

Signed-Off-By: Simon Ser <contact@emersion.fr>
Reviewed-by: Olivier Fourdan <ofourdan@redhat.com>