The code building the mode-list does the following to deal with screen
rotation:

    if (need_rotate || xwl_output->rotation & (RR_Rotate_0 | RR_Rotate_180)) {
        mode_width = xwl_output->width;
        mode_height = xwl_output->height;
    } else {
        mode_width = xwl_output->height;
        mode_height = xwl_output->width;
    }

This means we need to do something similar in xwl_output_set_emulated_mode()
to determine if the mode being set is the actual (not-emulated) output mode
and we this should remove any emulated modes set by the client.

All callers of xwl_output_set_emulated_mode always pass a mode pointer
to a member of xwl_output->randr_output->modes, so we do not need to
duplicate this code, instead we can simply check that the passed in mode
is modes[0] which always is the actual output mode.

Acked-by: Olivier Fourdan <ofourdan@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>