Hi lohith,
I understand you did not find any documentation for the L1 regularization while you find the below documentation for the L2 Regularization: https://www.mathworks.com/help/deeplearning/ref/nnet.cnn.layer.layer.setl2factor.html
In the Statistics and Machine Learning Toolbox, functions like lassoglm directly implement Lasso regression for linear models and generalized linear models, respectively.
You can find the documentation here: Lasso or elastic net regularization for generalized linear models - MATLAB lassoglm - MathWorks India
I hope it helps!