zink: fix free of ralloced pointer

When we alloc with ralloc, we also need to free with it.

But let's take a step back here; we don't just need to use ralloc, we
also need to destroy all other screen-resources. So let's call the
destructor here instead.

Fixes: 2643f9ed28 ("zink: ralloc screen objects")
Reviewed-By: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9647>

src/gallium/drivers/zink/zink_screen.c

@@ -1461,7 +1461,7 @@ zink_drm_create_screen(int fd, const struct pipe_screen_config *config)
 
    if (ret && !ret->info.have_KHR_external_memory_fd) {
       debug_printf("ZINK: KHR_external_memory_fd required!\n");
-      free(ret);
+      zink_destroy_screen(&ret->base);
       return NULL;
    }