As part of the new requirement to understand the reason for the
wifi hang the data need to be collected from the required modules
which will help in root-causing the reason for the hang.
Add the infrastructure so that the required modules can register for
this hang event notifier chain.
Change-Id: I32f1365eec1ad7d6e19be95e8faf9a980d054b76
CRs-Fixed: 2648304
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