A hotplug handler is allocated by calling qdf_cpuhp_register. However,
qdf_cpuhp_unregister does not free the previously allocated memory. Free
the hotplug handler in qdf_cpuhp_unregister.
Change-Id: I1663f5ea29a8630b42be33abd824135b0fbe4845
CRs-Fixed: 2141119
Currently, there are two consumers of the Linux kernel CPU hotplug APIs.
Besides being problematic for not being operating system agnostic,
different versions of the Linux kernel export different CPU hotplug
APIs. In order to consolidate the various abstractions for different
operating systems and API versions, create a CPU hotplug abstraction in
QDF.
Change-Id: Ib17c6e3ed3a87a90a82d909a6c493360cab27855
CRs-Fixed: 2132632
