Added support for delayed ack.
https://www.codeaurora.org/cgit/quic/la/kernel/msm/commit/?h=kk_2.7-stable&id=73989a4b345bba0efca96cc86b0258e83884ff63
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: oppo-source/Find5-Kernel-Source-4.2@c7b44a4
Original author: huanggd @oppo-source

Change-Id: I08bbbdd49c8764a3180c0d7a9197d2b9c8112d81
Signed-off-by: Luis Cruz <ljc2491@gmail.com>