Bugfix: deepseek benchmark names conflict (#725)

Summary
Deepseek currently registers two benchmarks using the same identifier,
causing a naming conflict.

Change
Rename each benchmark so that both have unique, descriptive names.
Co-authored-by: Hongtao Zhang <hongtaozhang@microsoft.com>

superbench/benchmarks/model_benchmarks/megatron_gpt3.py

@@ -749,7 +749,7 @@ def _cal_params_count(self):
     'megatron-deepseek-v2', MegatronGPT, parameters='--model=deepseek', platform=Platform.ROCM
 )
 BenchmarkRegistry.register_benchmark(
-    'megatron-deepseek-v2',
+    'megatron-deepseek-v2-lite',
     MegatronGPT,
     parameters=(
         '--model=deepseek '