pan/kmod: Fix a syncobj leak in the panthor backend

Make sure we release the syncobj attached to the BO if the object is
sharable.

Fixes: 97f6a62f7e ("pan/kmod: Add a backend for panthor")
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Acked-by: Constantine Shablia <constantine.shablya@collabora.com>
Reviewed-by: Antonino Maniscalco <antonino.maniscalco@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28926>

src/panfrost/lib/kmod/panthor_kmod.c

@@ -309,6 +309,12 @@ err_free_bo:
 static void
 panthor_kmod_bo_free(struct pan_kmod_bo *bo)
 {
+   struct panthor_kmod_bo *panthor_bo =
+      container_of(bo, struct panthor_kmod_bo, base);
+
+   if (!bo->exclusive_vm)
+      drmSyncobjDestroy(bo->dev->fd, panthor_bo->sync.handle);
+
    drmCloseBufferHandle(bo->dev->fd, bo->handle);
    pan_kmod_dev_free(bo->dev, bo);
 }