mm/demotion: build demotion targets based on explicit memory tiers

mm/demotion: build demotion targets based on explicit memory tiers

This patch switch the demotion target building logic to use memory tiers
instead of NUMA distance.  All N_MEMORY NUMA nodes will be placed in the
default memory tier and additional memory tiers will be added by drivers
like dax kmem.

This patch builds the demotion target for a NUMA node by looking at all
memory tiers below the tier to which the NUMA node belongs.  The closest
node in the immediately following memory tier is used as a demotion
target.

Since we are now only building demotion target for N_MEMORY NUMA nodes the
CPU hotplug calls are removed in this patch.

Link: https://lkml.kernel.org/r/20220818131042.113280-6-aneesh.kumar@linux.ibm.com
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Acked-by: Wei Xu <weixugc@google.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Bharata B Rao <bharata@amd.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Hesham Almatary <hesham.almatary@huawei.com>
Cc: Jagdish Gediya <jvgediya.oss@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Tim Chen <tim.c.chen@intel.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>