ksmbd: Implements sess->ksmbd_chann_list as xarray

[ Upstream commit 1d9c4172 ]

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>
Stable-dep-of: f5c779b7 ("ksmbd: fix racy issue from session setup and logoff")
Signed-off-by: Sasha Levin <sashal@kernel.org>