ksmbd: Use unsafe_memcpy() for ntlm_negotiate

commit dfd046d0 upstream.

rsp buffer is allocated larger than spnego_blob from
smb2_allocate_rsp_buf().

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>