Performance: Optimal minfree values for 32bit devices

Existing boundary (both low and high) values for
OOM min free, are fine tuned to suit lowmemorykiller
behavior.

For 64 bit builds, no change in values or logic for now.

For 32 bit builds, this change makes lowmemorykiller
minfree values optimal. Arrived at these values after
evaluating UX and launch latencies.

Change-Id: Ia797ead2d330ec3347ee964ac5ec3dd6513134a4