Define cache module code required for RDK-B statistics :
a. Objects to maintain tx and rx rate related statistics
b. Interface objects to be use by dp while pushing stats to module
c. Northbound interaction specific IOCTL structures/enums
d. WDI handlers for southbound interaction from dp to stats module.
CRs-Fixed: 2407888
Change-Id: I50b1461bc415e957d224bb1ec56e5e94cd833c27