samples: wifi: esp32s2_saola: reduce RAM usage

This modification frees up around ~10kB of RAM and make sample code
working again.

1) Reduced net packet size and count.
2) Increase Wi-Fi heap to avoid memory allocation failure.
3) Keep log as minimal.

Signed-off-by: Sylvio Alves <sylvio.alves@espressif.com>

samples/net/wifi/boards/esp32s2_saola.conf

@@ -1,11 +1,12 @@
 CONFIG_WIFI=y
-CONFIG_HEAP_MEM_POOL_SIZE=32768
+CONFIG_HEAP_MEM_POOL_SIZE=34816
+
+# decrease packet count and size to save RAM
+CONFIG_NET_PKT_RX_COUNT=7
+CONFIG_NET_PKT_TX_COUNT=7
+CONFIG_NET_BUF_RX_COUNT=7
+CONFIG_NET_BUF_TX_COUNT=7
 
-# when enabling NET_SHELL, the following
-# helps to optimize memory footprint
-CONFIG_ESP32_WIFI_STATIC_RX_BUFFER_NUM=8
-CONFIG_ESP32_WIFI_DYNAMIC_RX_BUFFER_NUM=8
-CONFIG_ESP32_WIFI_DYNAMIC_TX_BUFFER_NUM=8
 CONFIG_ESP32_WIFI_IRAM_OPT=n
 CONFIG_ESP32_WIFI_RX_IRAM_OPT=n
 
@@ -15,5 +16,7 @@ CONFIG_NET_L2_ETHERNET=y
 CONFIG_NET_IPV6=n
 CONFIG_NET_IPV4=y
 CONFIG_NET_DHCPV4=y
+CONFIG_ESP32_WIFI_STA_AUTO_DHCPV4=y
 
+CONFIG_LOG_MODE_MINIMAL=y
 CONFIG_NET_LOG=y