Update on "add qnnpack path for hardtanh"

Summary:

Adds a QNNPack path for the clamp kernel, which is useful for
hardtanh.

Test Plan:

python test/test_quantized.py TestQNNPackOps.test_hardtanh

Reviewers:

Subscribers:

Tasks:

Tags:

Differential Revision: [D20778588](https://our.internmc.facebook.com/intern/diff/D20778588)

[ghstack-poisoned]

test/quantization/test_quantized_op.py

@@ -463,6 +463,8 @@ def test_qclamp(self, X, min_val, max_val):
            min_val=hu.floats(-1e6, 1e6, allow_nan=False, allow_infinity=False),
            max_val=hu.floats(-1e6, 1e6, allow_nan=False, allow_infinity=False))
     def test_hardtanh(self, X, min_val, max_val):
+        if 'fbgemm' not in torch.backends.quantized.supported_engines:
+            return
         with override_quantized_engine('fbgemm'):
             X, (scale, zero_point, torch_type) = X
 
@@ -2839,6 +2841,8 @@ def test_qhardsigmoid(self, X):
            min_val=hu.floats(-1e6, -9.999999974752427e-07, allow_nan=False, allow_infinity=False),
            max_val=hu.floats(9.999999974752427e-07, 1e6, allow_nan=False, allow_infinity=False))
     def test_hardtanh(self, X, min_val, max_val):
+        if 'qnnpack' not in torch.backends.quantized.supported_engines:
+            return
         with override_quantized_engine('qnnpack'):
             X, (scale, zero_point, torch_type) = X