block: Switch from BFQ-v7r3 to BFQ-v7r4

. BUGFIX: Removed the check on NCQ capability before incrementing or
  decrementing counters related to the throughput-boosting mechanism
  used in case of NCQ-capable drives. In fact, the NCQ detection logic
  may cause the value of the associated variable to fluctuate, therefore
  leading to asymmetric increments or decrements.
. IMPROVEMENT: Removed a redundant condition from the logical expression
  used to establish whether a queue must benefit from idling.

Signed-off-by: Paolo Valente <paolo.valente@unimore.it>
Signed-off-by: Arianna Avanzini <avanzini.arianna@gmail.com>
Merge branch 'bfq-3.14' into pf-3.14