kernel: udp: Set SOCK_RCU_FREE earlier in udp_lib_get_port()

In the Linux kernel, the following vulnerability has been resolved: udp: Set SOCKRCUFREE earlier in udplibgetport. syzkaller triggered the warning 0 in udpv4earlydemux. In udpv46earlydemux and sklookup, we do not touch the refcount of the looked-up sk and use sockpfree as skb-destructor, so we...