[float8] Fix module filter function (#1391)

In a prior PR we added the `_init_filter_fn()` to configure a module
filter function at Float8 component init time, but didn't actually use
it. This went unnoticed because the existing module filter
(`partial(module_filter_fn, filter_fqns=self.filter_fqns)` behaves the
same way except for the case where the user uses `auto_filter_small_kn`.
In this PR we fix that by using the `self.filter_fn`.

## Test plan
- Test auto_filter_small_kn and verify the wk/wv are filtered for Llama3
8b: `NGPU=4
CONFIG_FILE="./torchtitan/models/llama3/train_configs/llama3_8b.toml"
./run_train.sh --training.steps=100 --training.compile
--model.converters="float8" --float8.recipe_name="rowwise"
--parallelism.tensor_parallel_degree=2
--float8.filter_fqns="auto_filter_small_kn"
--model.print-after-conversion`
- Test without auto_filter_small_kn and verify all linears are
converted: `NGPU=4
CONFIG_FILE="./torchtitan/models/llama3/train_configs/llama3_8b.toml"
./run_train.sh --training.steps=100 --training.compile
--model.converters="float8" --float8.recipe_name="rowwise"
--parallelism.tensor_parallel_degree=2
--float8.filter_fqns="auto_filter" --model.print-after-conversion

Author: danielvegamyhre

torchtitan/components/quantization/float8.py

@@ -165,7 +165,7 @@ def convert(self, model: nn.Module):
         convert_to_float8_training(
             model,
             config=self.config,
-            module_filter_fn=partial(module_filter_fn, filter_fqns=self.filter_fqns),
+            module_filter_fn=self.filter_fn,
         )
         logger.info(
             "Swapped to Float8Linear layers with enable_fsdp_float8_all_gather="