ksmbd: fix out of bounds read in smb2_sess_setup

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix out of bounds read in smb2_sess_setup ksmbd does not consider the case of that smb2 session setup is in compound request. If this is the second payload of the compound, OOB read issue occurs while processing the first payload in the smb2_sess_setup().