examples: set correct CPU frequency in ethernet/iperf for ESP32-S2

examples/ethernet/iperf/sdkconfig.defaults

@@ -12,8 +12,4 @@ CONFIG_FREERTOS_USE_STATS_FORMATTING_FUNCTIONS=y
 
 CONFIG_ESPTOOLPY_FLASHSIZE_4MB=y
 
-# ESP32-specific
-CONFIG_ESP32_DEFAULT_CPU_FREQ_240=y
-CONFIG_ESP32_DEFAULT_CPU_FREQ_MHZ=240
-
 CONFIG_ESP_NETIF_TCPIP_ADAPTER_COMPATIBLE_LAYER=n

examples/ethernet/iperf/sdkconfig.defaults.esp32

@@ -0,0 +1,2 @@
+# ESP32-specific
+CONFIG_ESP32_DEFAULT_CPU_FREQ_240=y

examples/ethernet/iperf/sdkconfig.defaults.esp32s2

@@ -0,0 +1,2 @@
+# ESP32-S2-specific
+CONFIG_ESP32S2_DEFAULT_CPU_FREQ_240=y