Revert "mesa: unreference current winsys buffers when unbinding winsys buffers"

This reverts commit 12bf7cfe.

This commits caused lots of problems:
https://bugs.freedesktop.org/show_bug.cgi?id=110721
https://bugs.freedesktop.org/show_bug.cgi?id=110761

Fixes: 12bf7cfe ("mesa: unreference current winsys buffers when unbinding winsys buffers")
Pushing without review as we need to get it into next stable.

(cherry picked from commit 7fe5a8e8)