output type conversion fix (vllm-project#27159)

Author: jianyuh

vllm/model_executor/layers/batch_invariant.py

@@ -134,10 +134,7 @@ def matmul_kernel_persistent(
             bias_ptrs = bias_ptr + offs_cn
             bias = tl.load(bias_ptrs, mask=offs_cn < N, other=0.0).to(tl.float32)
             accumulator += bias
-        if c_ptr.dtype.element_ty == tl.float8e4nv:
-            c = accumulator.to(tl.float8e4nv)
-        else:
-            c = accumulator.to(tl.float16)
+        c = accumulator.to(c_ptr.dtype.element_ty)
         tl.store(c_ptrs, c, mask=c_mask)