[Misc] Nit fix for disaggregated_prefill and ascend_forward_context (#2097)

we recently added disaggregated_prefill and ascend_forward_context
feature by
ba3dfbd59e
and
df0ec55162.
This PR fix some nit introduced by them to make the code clear.
1. drop `current_platform` usage. It'll lead unknown circular import
error in some case
2. update `set_ascend_forward_context` function to make the logic clear.
for example, remove V0 support in this function.
3. Remove useless `self.local_rank_across_dp` in worker
4. Remove `soc_info.py` to use `get_ascend_soc_version` instead.
 

- vLLM version: v0.10.0
- vLLM main:
02f82fe438

Signed-off-by: wangxiyuan <wangxiyuan1007@gmail.com>

examples/disaggregated_prefill_v1/gen_ranktable.py

@@ -4,7 +4,7 @@ import os
 
 import torch.distributed as dist
 
-from vllm_ascend.soc_info import NPUSocInfo
+from vllm_ascend.utils import AscendSocVersion, init_ascend_soc_version, get_ascend_soc_version
 
 parser = argparse.ArgumentParser(
     description="Arguments of rank table generator", )
@@ -33,7 +33,9 @@ local_rank = os.environ.get("LOCAL_RANK")
 # This variable is set by torchrun,
 # and is different from WORLD_SIZE in gen_rank_table.sh.
 world_size = os.environ.get("WORLD_SIZE")
-soc_info = NPUSocInfo()
+
+init_ascend_soc_version()
+soc_info = get_ascend_soc_version()
 
 
 def get_cmd_stdout(cmd):
@@ -59,7 +61,7 @@ if local_rank == "0":
     for card_id in range(num_cards):
         for chip_id in range(chips_per_card):
             device_id = card_id * chips_per_card + chip_id
-            if soc_info.is_a3:
+            if soc_info == AscendSocVersion.A3:
                 device_ip = get_cmd_stdout(
                     f"{hccn_tool_path} -i {device_id} -vnic -g | grep ipaddr"
                 ).split(":")[1].strip()
@@ -79,7 +81,7 @@ if local_rank == "0":
                 "device_id": str(device_id),
                 "device_ip": str(device_ip),
             }
-            if soc_info.is_a3:
+            if soc_info == AscendSocVersion.A3:
                 device_info.update({
                     "super_pod_id": str(super_pod_id),
                     "super_device_id": str(super_device_id)