Update BFQ to v7r4

Budget Fair Queueing I/O Scheduler
==================================

This patchset introduces BFQ-v7r4 into Linux 3.4.0.
For further information: http://www.algogroup.unimo.it/people/paolo/disk_sched/.

CHANGELOG

v7r4:
. BUGFIX. Modified the code so as to be robust against late detection of
  NCQ support for a rotational device.
. BUGFIX. Removed a bug that hindered the correct throughput distribution
  on flash-based devices when not every process had to receive the same
  fraction of the throughput. This fix entailed also a little efficiency
  improvement, because it implied the removal of a short function executed
  in a hot path.
. CODESTYLE IMPROVEMENT: removed quoted strings split across lines.

Change-Id: Ib73ed68e47d714255347e71c5bc1392b04b95a7b