UBUNTU: hio: Update io stat accounting for 4.14

UBUNTU: hio: Update io stat accounting for 4.14

In 4.14-rc1 invflight accounting calls were updated to require a
request queue be passed, and part_(inc|dec)_in_flight() were
moved out of linux/genhd.h and are not exported to modules. Make
a couple of updates to cope with these changes:

 - Pass the rq to part_round_stats for 4.14 and later.

 - Use generic_(start|end)_io_acct() helpers for io accounting
   with 4.14 and later. These do exactly what was being done with
   the no-longer-exported interfaces.

Signed-off-by: Seth Forshee <seth.forshee@canonical.com>