Add support for PPP modems (#169)

* Add support for PPP modems

* Turn off DHCPC restore last IP until fixed for PPP

Author: me-no-dev

Diff for: configs/defconfig.common

@@ -56,14 +56,18 @@ CONFIG_LWIP_TCPIP_TASK_AFFINITY_CPU0=y
 CONFIG_LWIP_MAX_SOCKETS=16
 CONFIG_LWIP_IP_FORWARD=y
 CONFIG_LWIP_IPV4_NAPT=y
-CONFIG_LWIP_DHCP_RESTORE_LAST_IP=y
+CONFIG_LWIP_DHCP_RESTORE_LAST_IP=n
 CONFIG_LWIP_DHCP_OPTIONS_LEN=128
 CONFIG_LWIP_SNTP_MAX_SERVERS=3
 CONFIG_LWIP_SNTP_UPDATE_DELAY=10800000
 CONFIG_LWIP_DHCP_GET_NTP_SRV=y
 CONFIG_LWIP_IPV6_AUTOCONFIG=y
 CONFIG_LWIP_IPV6_DHCP6=y
 CONFIG_LWIP_IPV6_RDNSS_MAX_DNS_SERVERS=2
+CONFIG_LWIP_PPP_SUPPORT=y
+CONFIG_LWIP_PPP_NOTIFY_PHASE_SUPPORT=y
+CONFIG_LWIP_PPP_PAP_SUPPORT=y
+CONFIG_LWIP_PPP_ENABLE_IPV6=n
 CONFIG_MBEDTLS_PSK_MODES=y
 CONFIG_MBEDTLS_KEY_EXCHANGE_PSK=y
 CONFIG_MBEDTLS_CAMELLIA_C=y