fix overflow fp16 act woq int8

[leslie-fang-intel]

Fix issue #1662, the reference kernel implementation overflows with fp16 input data.

[pytorch-bot]

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🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/ao/1698

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❌ 7 New Failures

As of commit 0f1b413 with merge base 999b16d ():

NEW FAILURES - The following jobs have failed:

• PR Label Check / Check PR Labels (gh)
  Process completed with exit code 1.
• Run Regression Tests / test (CPU 2.4, linux.4xlarge, torch==2.4.0 --index-url https://download.pytorch.org/whl/cpu, cpu) / linux-job (gh)
  test/integration/test_integration.py::TestSubclass::test_int8_weight_only_quant_with_freeze_2_cpu
• Run Regression Tests / test (CPU 2.5.1, linux.4xlarge, torch==2.5.1 --index-url https://download.pytorch.org/whl/cpu, cpu) / linux-job (gh)
  test/integration/test_integration.py::TestSubclass::test_int8_weight_only_quant_with_freeze_2_cpu
• Run Regression Tests / test (CUDA 2.4, linux.g5.12xlarge.nvidia.gpu, torch==2.4.0, cuda, 12.1) / linux-job (gh)
  test/quantization/test_quant_api.py::TestQuantFlow::test_quantized_tensor_subclass_int8_wo
• Run Regression Tests / test (CUDA 2.5.1, linux.g5.12xlarge.nvidia.gpu, torch==2.5.1 --index-url https://download.pytorch... / linux-job (gh)
  test/quantization/test_quant_api.py::TestQuantFlow::test_quantized_tensor_subclass_int8_wo
• Run Regression Tests / test-nightly (CPU Nightly, linux.4xlarge, --pre torch==2.7.0.dev20250122 --index-url https://down... / linux-job (gh)
  test/integration/test_integration.py::TestSubclass::test_int8_weight_only_quant_with_freeze_2_cpu
• Run Regression Tests / test-nightly (CUDA Nightly, linux.g5.12xlarge.nvidia.gpu, --pre torch==2.7.0.dev20250122 --index-... / linux-job (gh)
  test/quantization/test_quant_api.py::TestQuantFlow::test_quantized_tensor_subclass_int8_wo

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