net: sched: gred: remove NULL check before free table->tab in gred_destroy()

The kfree invoked by gred_destroy_vq checks whether the input parameter
is empty. Therefore, gred_destroy() doesn't need to check table->tab.

Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
Link: https://lore.kernel.org/r/20220831041452.33026-1-shaozhengchao@huawei.com


Signed-off-by: Paolo Abeni <pabeni@redhat.com>