implementation of qmul using xnnpack (#86040)
Summary: implementation of qmul using xnnpack
Test Plan: buck run caffe2/test:quantization -- quantization.core.test_quantized_op.TestQNNPackOps
Reviewed By: digantdesai, kirklandsign
Differential Revision: D39701867
Pull Request resolved: https://github.com/pytorch/pytorch/pull/86040
Approved by: https://github.com/digantdesai
