[HMM v16 14/15] mm/hmm/devmem: device driver helper to hotplug ZONE_DEVICE memory v2

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 v16 14/15] mm/hmm/devmem: device driver helper to hotplug ZONE_DEVICE memory v2

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