lowmemorykiller: Fix high min-free values

AOSP commit 5a150e44 was supposed
to increase min-free levels for 64-bit only. Instead it increases
it for everyone. This restores previous values that are consistently
50% bigger than values used in KitKat. Values for two largest min-
free buckets are still overriden for 64-bit.

Change-Id: I8beca86d8b3a389e68e864143e241dd0b1531613