Add fusion for quantized linear (#25624)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/25624
First fuse the splitted op into aten::linear and then fuse
`dequant - aten::linear - quant` into quantized linear op
Test Plan:
python test/test_jit.py 'TestJit.quant_fusion'
Imported from OSS
Differential Revision: D17208891
fbshipit-source-id: 864b19fabab2e8e6f8f8ad35eb3dbbf2d5fdb8c4
