Multi-gen LRU: fix workingset accounting

On Android app cycle workloads, MGLRU showed a significant reduction in
workingset refaults although pgpgin/pswpin remained relatively unchanged. 
This indicated MGLRU may be undercounting workingset refaults.

This has impact on userspace programs, like Android's LMKD, that monitor
workingset refault statistics to detect thrashing.

It was found that refaults were only accounted if the MGLRU shadow entry
was for a recently evicted folio.  However, recently evicted folios should
be accounted as workingset activation, and refaults should be accounted
regardless of recency.

Fix MGLRU's workingset refault and activation accounting to more closely
match that of the conventional active/inactive LRU.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: ac35a4902374 ("mm: multi-gen LRU: minimal implementation")
Signed-off-by: Kalesh Singh <[email protected]>
Reported-by: Charan Teja Kalla <[email protected]>
Acked-by: Yu Zhao <[email protected]>
Cc: Brian Geffon <[email protected]>
Cc: Jan Alexander Steffens (heftig) <[email protected]>
Cc: Oleksandr Natalenko <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

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