Update QAT README.md (#2162)

Author: SalmanMohammadi

torchao/quantization/qat/README.md

@@ -115,10 +115,11 @@ To fake quantize embedding in addition to linear, you can additionally call
 the following with a filter function during the prepare step:
 
 ```
+from torchao.quantization.quant_api import _is_linear
 quantize_(
     m,
     IntXQuantizationAwareTrainingConfig(weight_config=weight_config),
-    filter_fn=lambda m, _: isinstance(m, torch.nn.Embedding),
+    filter_fn=lambda m, _: isinstance(m, torch.nn.Embedding) or _is_linear(m),
 )
 ```