drm/nouveau: use rcu in nouveau_gem_ioctl_cpu_prep
drm/nouveau: use rcu in nouveau_gem_ioctl_cpu_prep

With the conversion to the reservation api this should be safe.

Signed-off-by: Maarten Lankhorst <743c2818a341d71b99ed2b566f9f80c2fc288f93@canonical.com>
Acked-by: Ben Skeggs <d9f27fb07c1e9f131223ad827fa5179f3846c30b@redhat.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs