ksmbd: fix use-after-free in ksmbd_sessions_deregister()

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: fix use-after-free in ksmbd_sessions_deregister()

In multichannel mode, UAF issue can occur in session_deregister

when the second channel sets up a session through the connection of

the first channel. session that is freed through the global session

table can be accessed again through ->sessions of connection.