Notifier chains are simple function list executed when an event
occurs. In qdf block and atomic notifier chains are defined.
Blocking notifier chains can be used to invoke a list of functions
based on event in a process context wherein atomic notifier chain
can be used in an interrupt context.
Change-Id: I9020b9f19915e084b017932fb6d0bfad792d745c
CRs-Fixed: 2648224
