ksmbd: fix out of bounds in init_smb2_rsp_hdr()

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix out of bounds in init_smb2_rsp_hdr() If client send smb2 negotiate request and then send smb1 negotiate request, init_smb2_rsp_hdr is called for smb1 negotiate request since need_neg is set to false. This patch ignore smb1 packets after ->need_neg is set to false.