linux-cp: Add support for LACP packets

linux-cp: Add support for LACP packets

This patch adds support to mirror LACP packets between host and phy.
It is needed for the Sonic-VPP project to support LAG and allow Sonic
to run LACP in the control plane.

The change has 3 parts:

(1) Converted lip_punt_node to lip_punt_xc_inline, which now supports
the creation of two distinct nodes: lip_punt_node and lip_punt_xc_node.
lip_punt_node retains its original punt functionality.
lip_punt_xc_node supports both punt and x-connect between host & phy.

(2) Add 2 new API (and corresponding CLI) to the linux-cp plugin:
(A) lcp_ethertype_enable ("lcp ethertype enable <ethertype>")
(B) lcp_ethertype_get ("show lcp ethertype")

(3) Add UT to test the new functionality and API/CLI for LACP and LLDP.

Type: improvement

Change-Id: Iab66e3b29351dcf2c471babd4f1ef4bdd19da46e
Signed-off-by: Akeel Ali <[email protected]>