net/smc: fix wrong list_del in smc_lgr_cleanup_early

smc_lgr_cleanup_early() meant to delete the link
group from the link group list, but it deleted
the list head by mistake.

This may cause memory corruption since we didn't
remove the real link group from the list and later
memseted the link group structure.
We got a list corruption panic when testing:

[  231.277259] list_del corruption. prev->next should be ffff8881398a8000, but was 0000000000000000
[  231.278222] ------------[ cut here ]------------
[  231.278726] kernel BUG at lib/list_debug.c:53!
[  231.279326] invalid opcode: 0000 [#1] SMP NOPTI
[  231.279803] CPU: 0 PID: 5 Comm: kworker/0:0 Not tainted 5.10.46+ #435
[  231.280466] Hardware name: Alibaba Cloud ECS, BIOS 8c24b4c 04/01/2014
[  231.281248] Workqueue: events smc_link_down_work
[  231.281732] RIP: 0010:__list_del_entry_valid+0x70/0x90
[  231.282258] Code: 4c 60 82 e8 7d cc 6a 00 0f 0b 48 89 fe 48 c7 c7 88 4c
60 82 e8 6c cc 6a 00 0f 0b 48 89 fe 48 c7 c7 c0 4c 60 82 e8 5b cc 6a 0...