ksmbd: mark rejected cross-dialect bindings as signed

ksmbd: mark rejected cross-dialect bindings as signed

Binding an SMB 2.1 session to an SMB 3.x connection is invalid because the
dialects do not match. ksmbd returns STATUS_INVALID_PARAMETER. The check
fails before attaching the referenced session to the request, so the error
response lacks SMB2_FLAGS_SIGNED.

A client requiring signing checks this flag before handling the status and
reports STATUS_ACCESS_DENIED instead of STATUS_INVALID_PARAMETER. Preserve
the signed flag for a signed binding request rejected with
STATUS_INVALID_PARAMETER. The client can then apply the special error path
without attempting to validate a response using incompatible signing
algorithms.

This fixes smb2.session.bind_negative_smb2to3s.

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>