drm/v3d: Fix potential memory leak in the performance extension

In the Linux kernel, the following vulnerability has been resolved: drm/v3d: Fix potential memory leak in the performance extension If fetching of userspace memory fails during the main loop, all drm sync objs looked up until that point will be leaked because of the missing drm_syncobj_put. Fix it by exporting and using a common cleanup helper. (cherry picked from commit 484de39fa5f5b7bd0c5f2e2c5265167250ef7501)