9p: trans_fd/p9_conn_cancel: drop client lock earlier

stable inclusion
from stable-v5.10.156
commit f14858bc77c567e089965962877ee726ffad0556
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7MCG1

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f14858bc77c567e089965962877ee726ffad0556

--------------------------------

commit 52f1c45d upstream.

syzbot reported a double-lock here and we no longer need this
lock after requests have been moved off to local list:
just drop the lock earlier.

Link: https://lkml.kernel.org/r/20220904064028.1305220-1-asmadeus@codewreck.org


Reported-by:  <syzbot+50f7e8d06c3768dd97f3@syzkaller.appspotmail.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
Tested-by: Schspa Shi <schspa@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>