[qca-nss-ecm] ifdef'd all the PPPoE code.

* This will make it easy to remove PPPoE code from the compilation.
* Clean up unused code.

Change-Id: I84896e516421da2eb2f0bd53a65799a3301cca55
Signed-off-by: Murat Sezgin <msezgin@codeaurora.org>
6 files changed