LAG upgrade - 24: removing custom member port create API

Removed #custom #member #port #create / #remove API in LAG module. The custom member port entries are #embedded in the #standard #member #port entries and the standard member port create / remove API already handles the required functionality. Hence the redundant external API is being removed.

#LAG update 32 ...
[commit a494870f8213e5784c9f97e77db46899151af7e4] (https://github.com/nes-repo/NES-Open-Switch/commit/a494870f8213e5784c9f97e77db46899151af7e4)