drm/v3d: Validate passed in drm syncobj handles in the timestamp extension

If userspace provides an unknown or invalid handle anywhere in the handle
array the rest of the driver will not handle that well.

Fix it by checking handle was looked up successfully or otherwise fail the
extension by jumping into the existing unwind.

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/20240711135340.84617-5-tursulin@igalia.com