kABI: Prepare mm SST for kABI Lockdown

The following MM structures are impacted by symbols that have been approved for kabi:

core_state
core_thread
dev_pagemap
dev_pagemap_ops
ldt_struct
mempolicy
mempool_s
mm_rss_stat
mm_struct
page
page_frag
percpu_cluster
readahead_control
reclaim_state
shrink_control
shrinker
swap_cluster_info
swap_cluster_list
swap_info_struct
sysv_shm
task_rss_stat
tlbflush_unmap_batch
vm_area_struct
vm_fault
vm_operations_struct
vm_struct
vm_userfaultfd_ctx
vmacache
vmem_altmap
wait_page_queue
cgroup structs (already hidden)

Pad some of these structs (and hide others) to ensure stability, visibility, and allow for easier z-stream backports when impacted by kABI lockdown.

We will have to go back before the stablelist is computed and do any padding for newly acked symbols. We can also pad ENUMs and look into inlined functions on the second pass.

Upstream-Status: RHEL-Only

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2048328

Signed-off-by: Nico Pache npache@redhat.com