example: fix led strip memory overwrite before trans done

Closes https://github.com/espressif/esp-idf/issues/11487

examples/peripherals/rmt/led_strip/main/led_strip_example_main.c

@@ -118,9 +118,11 @@ void app_main(void)
             }
             // Flush RGB values to LEDs
             ESP_ERROR_CHECK(rmt_transmit(led_chan, led_encoder, led_strip_pixels, sizeof(led_strip_pixels), &tx_config));
+            ESP_ERROR_CHECK(rmt_tx_wait_all_done(led_chan, portMAX_DELAY));
             vTaskDelay(pdMS_TO_TICKS(EXAMPLE_CHASE_SPEED_MS));
             memset(led_strip_pixels, 0, sizeof(led_strip_pixels));
             ESP_ERROR_CHECK(rmt_transmit(led_chan, led_encoder, led_strip_pixels, sizeof(led_strip_pixels), &tx_config));
+            ESP_ERROR_CHECK(rmt_tx_wait_all_done(led_chan, portMAX_DELAY));
             vTaskDelay(pdMS_TO_TICKS(EXAMPLE_CHASE_SPEED_MS));
         }
         start_rgb += 60;