staging: android: lowmemorykiller: Don't count reserved free memory

The amount of reserved memory varies between devices. Subtract it
here to reduce the amount of devices specific tuning needed for the
minfree values.

Change-Id: I466ae8b18f5972f6f6d8b5a7d8c4ae69660de53a
Signed-off-by: Arve Hjønnevåg <arve@android.com>
adapted from Linux 3.4 Android Kernel Common

Signed-off-by: faux123 <reioux@gmail.com>
ramfs : renamed busybox in ramfs to "mount" and symbolically linked "umount" to it so busybox updater won't see 2 busybox installations (those are needed for cifs support)