graph: define API

graph: define API

Graph architecture abstracts the data processing functions as
"node" and "link" them together to create a complex "graph" to enable
reusable/modular data processing functions.

These APIs enables graph framework operations such as create, lookup,
dump and destroy on graph and node operations such as clone,
edge update, and edge shrink, etc. The API also allows creating the
stats cluster to monitor per graph and per node stats.

This patch defines the public API for graph support.
This patch also adds support for the build infrastructure and
update the MAINTAINERS file for the graph subsystem.

Signed-off-by: Jerin Jacob <jerinj@marvell.com>
Signed-off-by: Kiran Kumar K <kirankumark@marvell.com>
Signed-off-by: Pavan Nikhilesh <pbhagavatula@marvell.com>
Signed-off-by: Nithin Dabilpuram <ndabilpuram@marvell.com>