[Perf] Reduce peak memory usage of llama (#10339)

Signed-off-by: andoorve <[email protected]>

Author: andoorve

vllm/model_executor/models/llama.py

@@ -90,8 +90,8 @@ def __init__(
         self.act_fn = SiluAndMul()
 
     def forward(self, x):
-        gate_up, _ = self.gate_up_proj(x)
-        x = self.act_fn(gate_up)
+        x, _ = self.gate_up_proj(x)
+        x = self.act_fn(x)
         x, _ = self.down_proj(x)
         return x