[https://nvbugs/5582091][test] increase warmup times in testing for multi-gpu cases (NVIDIA#9578)

Signed-off-by: Ruodi Lu <ruodil@users.noreply.github.com>
Co-authored-by: Ruodi Lu <ruodil@users.noreply.github.com>

Author: ruodil

tests/integration/defs/perf/test_perf.py

@@ -1732,6 +1732,8 @@ def get_trtllm_bench_command(self, engine_dir):
             benchmark_cmd += [f"--pp={self._config.pp_size}"]
         if self._config.streaming == "streaming":
             benchmark_cmd += [f"--streaming"]
+        if self._config.num_gpus > 1:
+            benchmark_cmd += [f"--warmup={2 * self._config.num_gpus}"]
 
         #Add extra-llm-api-config.yml for pytorch backend and tensorrt backend with extra flag
         if self._config.backend == "pytorch" or (self._config.backend == ""