ipv6: mcast: Simplify mld_clear_{report|query}()

Use __skb_queue_purge() instead of re-implementing it. Note that it uses
kfree_skb_reason() instead of kfree_skb() internally, and pass
SKB_DROP_REASON_QUEUE_PURGE drop reason to the kfree_skb tracepoint.

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Reviewed-by: Hangbin Liu <liuhangbin@gmail.com>
Link: https://patch.msgid.link/20250715120709.3941510-1-yuehaibing@huawei.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>