[qca-nss-ecm] Use the common hierarchy construct fucntion for IPv6

* Removed the IPv6 specific hierarchy construct function.
* Reworked the ecm_interface version of the function to be used
  by both IPv4 and IPv6.
* Implement a new ARP request send function.

Change-Id: I29f8bf979d40a9ad437dc0ee7e7c623b021967e5
Signed-off-by: Murat Sezgin <msezgin@codeaurora.org>
8 files changed