ci/riscv: fix unused var in esp_twai.c

This is to fix issue in [this log](https://github.com/apache/nuttx/actions/runs/9173629303/job/25222879619):

```
Configuration/Tool: esp32c3-generic/twai esp32c6-devkitm/twai esp32c6-devkitc/twai  esp32h2-devkit/twai
Error: common/espressif/esp_twai.c:242:7: error: variable 'ret' set but not used [-Werror=unused-but-set-variable]
```

Signed-off-by: Yanfeng Liu <[email protected]>

Author: yf13

arch/risc-v/src/common/espressif/esp_twai.c

@@ -251,7 +251,7 @@ static void esp_twai_reset(struct can_dev_s *dev)
   flags = enter_critical_section();
 
   ret = twai_hal_init(&priv->ctx, &hal_config);
-  assert(ret);
+  ASSERT(ret);
   twai_hal_configure(&priv->ctx, &priv->t_config, &f_config,
                      TWAI_DEFAULT_INTERRUPTS, 0);