Bismillaah-ir-Rahmaan-ir-Raheem.

Wa 'Alaykumussalam wa Rahmatullaahi wa Barakaatuh.

If a man calls his wife mother, or says "you are like a mother to me", the situation will be dependent on his niyyah. If his intention was to honour her then there will be no penalty. (Hidayah)
Therefore addressing one's wife by mother by mistake or jokingly, will not entail any penalty.

And Allaah knows best.

Wassalam