Only MADV_RANDOM for low RAM devices

Added logic to do MADV_RANDOM only for low ram devices since this
hurts performance on high end devices.

Test: build and flash
Bug: 63178181

(cherry picked from commit 72662a63a7fe2ff2e096017628af1a89fdd7a5ca)

Change-Id: I8f73a9b3d0133963fb709b1fa6491931f535a1b5
1 file changed