Revert "Added Fast Random generator support (frandom)"

This reverts commit 12074cc279fc6583e020a77662ae4092af16ca73.
Added whiteback tweak during screen on/off (franco)

Signed-off-by: Keff <funnykeff91@gmail.com>
mm/writeback: some adjustment

Signed-off-by: Keff <funnykeff91@gmail.com>