mm: writeback: every 500ms the writeback daemon kicks in and flushes …
…the dirty pages into disk. Thats not very pleasant for performance and *maybe* battery. This patch disables the writeback function while the screen is on, and enables it back when the screen is off to flush all the dirty pages. In my real world usage testing I notice a slight bump in smoothness and performance while using the device.

Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
Signed-off-by: erik96 <ariesrik96@gmail.com>
Added dynamic fsync v1.1 (Credits faux123)

Conflicts:

	fs/sync.c
changes
Update dynamic fsync to latest upstream version

Credits to faux123
dynamic fsync: 3.0 Kernel fixup