samples: zperf: Add STM32 eth_tx_async mode test

enable STM32 etc_tx_async mode for testing in CI

Signed-off-by: WenBin Zhang <freey7955@gmail.com>
diff --git a/samples/net/zperf/sample.yaml b/samples/net/zperf/sample.yaml
index 8124d75..256c3e8 100644
--- a/samples/net/zperf/sample.yaml
+++ b/samples/net/zperf/sample.yaml
@@ -17,6 +17,10 @@
     platform_allow: qemu_x86
     extra_configs:
       - CONFIG_NET_ZPERF_SERVER=n
+  sample.net.zperf.async_tx.stm32:
+    filter: dt_compat_enabled("st,stm32-ethernet") and CONFIG_ETH_STM32_HAL_API_V2
+    extra_configs:
+      - CONFIG_ETH_STM32_HAL_TX_ASYNC=y
   sample.net.zperf_st:
     harness: console
     harness_config: