Currently syncpoints are not locked by mutex and this causes races
if we are aggressively freeing and allocating syncpoints.

This patch adds missing mutex protection to syncpoint structures.
Signed-off-by: Arto Merilainen <amerilainen@nvidia.com>
Reviewed-by: Shridhar Rasal <srasal@nvidia.com>
Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
[treding@nvidia.com: use better label names, don't reset local variable]
Signed-off-by: Thierry Reding <treding@nvidia.com>