net/liquidio: add APIs for SG list

net/liquidio: add APIs for SG list

Add APIs to setup and free Scatter-Gather list. SG list is used while
sending packets with multiple segments.

Signed-off-by: Shijith Thotton <shijith.thotton@caviumnetworks.com>
Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
Signed-off-by: Derek Chickles <derek.chickles@caviumnetworks.com>
Signed-off-by: Venkat Koppula <venkat.koppula@caviumnetworks.com>
Signed-off-by: Srisivasubramanian S <ssrinivasan@caviumnetworks.com>
Signed-off-by: Mallesham Jatharakonda <mjatharakonda@oneconvergence.com>