zink: don't use set_foreach_remove with dmabuf_exports

foreach_remove cannot be used if the set ever has members deleted,
and this set may have deleted members

Fixes: 7b7a581a52 ("zink: prune dmabuf export tracking when adding resource binds")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28464>

src/gallium/drivers/zink/zink_batch.c

@@ -758,7 +758,7 @@ submit_queue(void *data, void *gdata, int thread_index)
 
    unsigned i = 0;
    VkSemaphore *sem = bs->signal_semaphores.data;
-   set_foreach_remove(&bs->dmabuf_exports, entry) {
+   set_foreach(&bs->dmabuf_exports, entry) {
       struct zink_resource *res = (void*)entry->key;
       for (; res; res = zink_resource(res->base.b.next))
          zink_screen_import_dmabuf_semaphore(screen, res, sem[i++]);
@@ -766,6 +766,7 @@ submit_queue(void *data, void *gdata, int thread_index)
       struct pipe_resource *pres = (void*)entry->key;
       pipe_resource_reference(&pres, NULL);
    }
+   _mesa_set_clear(&bs->dmabuf_exports, NULL);
 
    bs->usage.submit_count++;
 end: