[Kernel] add l2norm triton kernel (#4595)

### What this PR does / why we need it?
This pull request introduces an L2 normalization kernel implemented in
Triton, specifically optimized for Ascend NPUs.
### Does this PR introduce _any_ user-facing change?
No, this PR does not introduce any user-facing changes.
### How was this patch tested?

- vLLM version: v0.13.0
- vLLM main:
bc0a5a0c08

---------

Signed-off-by: Ascendyh <hw7osiris@outlook.com>
Co-authored-by: Mengqing Cao <cmq0113@163.com>

vllm_ascend/ops/triton/fla/chunk.py

@@ -13,13 +13,13 @@ from typing import Optional
 
 import torch
 from einops import rearrange
-from vllm.model_executor.layers.fla.ops.l2norm import l2norm_fwd
 from vllm.model_executor.layers.fla.ops.utils import SUPPRESS_LEVEL
 
 from .chunk_delta_h import chunk_gated_delta_rule_fwd_h
 from .chunk_o import chunk_fwd_o
 from .chunk_scaled_dot_kkt import chunk_scaled_dot_kkt_fwd
 from .cumsum import chunk_local_cumsum
+from .l2norm import l2norm_fwd
 from .solve_tril import solve_tril
 from .utils import input_guard
 from .wy_fast import recompute_w_u_fwd