nouveau: fix screen creation failure paths

nouveau: fix screen creation failure paths

The winsys layer would attempt to cleanup the nouveau_device if screen
init failed, however, in most paths the pipe driver would have already
destroyed it, resulting in accesses to freed memory etc.

This commit fixes the problem by allowing the winsys to detect whether
the pipe driver's destroy function needs to be called or not.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Tested-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>