wifi: esp32: add config to enable automatic DHCPV4 negotiation

ESP32 wifi connection uses Zephyr's net stack. Once WiFi connects
in station mode, is requires the application to handle DHCPv4
negotiation. This PR adds support to automatic negotiation by
handling the dhcpv4 calls in driver layer.

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