[quant][graphmode][fx][fp16] Add fp16 support for silu (#52865)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/52865
Test Plan:
python test/test_quantization.py TestQuantizeFxOps.test_silu
Imported from OSS
Reviewed By: vkuzo
Differential Revision: D26672270
fbshipit-source-id: a6a6ab58c347a56f0ded612b2e0a3e2230a91d9e
