ksmbd: limit read/write/trans buffer size not to exceed 8MB

mainline inclusion
from mainline-5.15-rc7
commit 4bc59477
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I60T7G
CVE: NA

Reference: https://git.kernel.org/torvalds/linux/c/4bc59477c329



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ksmbd limit read/write/trans buffer size not to exceed maximum 8MB.
And set the minimum value of max response buffer size to 64KB.
Windows client doesn't send session setup request if ksmbd set max
trans/read/write size lower than 64KB in smb2 negotiate.
It means windows allow at least 64 KB or more about this value.

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Zhong Jinghua <zhongjinghua@huawei.com>