CHROMIUM: clocksource: allow clocksources to be selected earlier during boot

Global and per-CPU timers ought to be initialized once SMP initialization
is complete.  Although the clocksources associated with these timers may
not be registered until later in the boot process, they should be ready
to go once registered.  We'd like to stop using the super low-resolution
boot clocksource (jiffies) as soon as possible since devices may rely on
accurate timekeeping while being brought up during boot, so move
clocksource_done_booting() to arch_initcall time so that we can switch
to a higher-resolution clocksrouce earlier in the boot process.

TEST=Pit and Lumpy both still boot reliably.  Boot time on Pit improves
considerably:
Before: [    3.032967] VFS: Mounted root ...
After:  [    1.855936] VFS: Mounted root ...
Lumpy boot time improves very slightly:
Before: [    1.786347] VFS: Mounted root ...
After:  [    1.754297] VFS: Mounted root ...

Signed-off-by: Andrew Bresticker <abrestic@chromium.org>
Reviewed-by: Sonny Rao <sonnyrao@chromium.org>
Reviewed-by: Sameer Nanda <snanda@chromium.org>
Signed-off-by: Luis Cruz <ljc2491@gmail.com>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
kswapd: Introduce congestion_wait_kswapd

congestion_wait for kswapd is similar to congestion_wait, the vital
difference is that congestion_wait_kswapd uses schedule_timeout
instead of io_schedule_timeout (which can cause IO wait conditions,
due to nr_iowait usage).

Derived from: https://github.com/oppo-source/Find5-Kernel-Source-4.2/commit/c7b44a43a970b699ecd68655bd6f83a8fbb3d74d
Original author: huanggd @oppo-source

Signed-off-by: Luis Cruz <ljc2491@gmail.com>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>