CS_P_ESP_LWIP -> CS_P_ESP8266;add CS_P_NXP_KINETIS

LWIP part has been finally fully split from the ESP part, and ESP
platform defs reduced to bare minimum. It is now possible to use LWIP
in either low-level or socket mode without any ESP dependencies,
and NXP Kinetis platform is the first to make use of it.

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