cm: Squashed commit of display-rtio patches

SAMBAR-275

cm: Create cgroups for BFQIO

 * This creates the interface for a new ioprio management system
   which dramatically boosts performance and interactivity across
   the entire system.

Change-Id: I3c402dd2cf6ed0a356a828257c2f373800f6a6cf

cm: Set IOPS mode for CFQ and BFQ automatically

 * Always set slice_idle to 0 for CFQ and BFQ (IOPS mode).
   This is a guaranteed performance boost for nonrotational storage
   and is also the new default in Linux 4.2+

Change-Id: Id271a4283219beb272c174de0e452c6c42c4e572

cm: Remove xattr option from bfqio cgroup

 * This was leftover from testing and breaks the feature when running
   on older kernels which don't support it.

Change-Id: Idb959b37b88238aee87c221d6accc899bf497aea

cm: Clean up cgroups

 * Remove unnecessary intermediate groups which are more harmful than
   helpful in some cases.
 * Remove weights, we're not using these.
 * Lock down the display group to system only.

Change-Id: I3a848fcc32459b53fa92317c253a20399637033e

cm: Clean up cgroups even more!

 * Only one is needed!

Change-Id: Ib79864bf2b7a3d86a2bad91de01a9b82279f4a91