drm/v3d: Fix potential memory leak in the timestamp 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.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Fixes: 9ba0ff3e ("drm/v3d: Create a CPU job extension for the timestamp query job")
Cc: Maíra Canal <mcanal@igalia.com>
Cc: Iago Toral Quiroga <itoral@igalia.com>
Cc: stable@vger.kernel.org # v6.8+
Reviewed-by: Maíra Canal <mcanal@igalia.com>
Signed-off-by: Maíra Canal <mcanal@igalia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240711135340.84617-3-tursulin@igalia.com


(cherry picked from commit 753ce4fea62182c77e1691ab4f9022008f25b62e)
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>