[HMM 13/15] mm/hmm/devmem: device memory hotplug using ZONE_DEVICE v3

This introduce a simple struct and associated helpers for device driver to use when hotpluging un-addressable device memory as ZONE_DEVICE. It will find a unuse physical address range and trigger memory hotplug for it which allocates and initialize struct page for the device memory. Changed since

[HMM 13/15] mm/hmm/devmem: device memory hotplug using ZONE_DEVICE v3

This introduce a simple struct and associated helpers for device driver to use when hotpluging un-addressable device memory as ZONE_DEVICE. It will find a unuse physical address range and trigger memory hotplug for it which allocates and initialize struct page for the device memory. Changed since