ksmbd: Implements sess->ksmbd_chann_list as xarray

mainline inclusion
from mainline-v6.3-rc1
commit 1d9c4172
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7CETC
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1d9c4172110e645b383ff13eee759728d74f1a5d



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For some ops on channel:
1. lookup_chann_list(), possibly on high frequency.
2. ksmbd_chann_del().

Connection is used as indexing key to lookup channel, in that case,
linear search based on list may suffer a bit for performance.

Implements sess->ksmbd_chann_list as xarray.

Signed-off-by: Dawei Li <set_pte_at@outlook.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: ZhaoLong Wang <wangzhaolong1@huawei.com>