Update ipadapter to the latest net API in Zephyr
Update ipadapter to the latest net API in Zephyr

The Zephyr build is broken after updating to latest Zephyr
1.8 because the net_buf API has changed.

Change-Id: I135f33bcc79627358b00c6a130c9b35bebedfec3
Signed-off-by: Jimmy Huang <17b2f82a731dc28428cf577995da8b43f2f13d79@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/20771
Reviewed-by: Kishen Maloor <c62ddea3cd661a9268bff15f07fc2229cdc9ac02@intel.com>
Tested-by: Kishen Maloor <c62ddea3cd661a9268bff15f07fc2229cdc9ac02@intel.com>

iotivity/iotivity-constrained,iotivity/iotivity-constrained,iotivity/iotivity-constrained,iotivity/iotivity-constrained