ANDROID: GKI: fix ABI diffs caused by ION heap and pool vmstat additions

New nr_ion_heap and nr_ion_heap_pool fields in vmstat file cause ABI
differences. Fix them by adding the fields.

Bug: 110330255
Bug: 130198686
Bug: 153442668
Test: boot
Signed-off-by: Minchan Kim <minchan@google.com>
(cherry picked from commit 8f76a3ed2a76492deba9edebc990cac3b32f78be)
Signed-off-by: Martin Liu <liumartin@google.com>
[surenb: cherry picked and trimmed the original patch to include only
necessary changes to resolve ABI diff for node_stat_item enum]

Bug: 149182139
Test: build and boot
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Change-Id: I82b43bd3d94b950bd266aa53a3794182604a52d0