Merge remote-tracking branch 'remotes/jnsnow/tags/ide-pull-request' into staging

# gpg: Signature made Wed 10 Feb 2016 19:23:29 GMT using RSA key ID AAFC390E
# gpg: Good signature from "John Snow (John Huston) <[email protected]>"

* remotes/jnsnow/tags/ide-pull-request:
  ahci: prohibit "restarting" the FIS or CLB engines
  ahci: explicitly reject bad engine states on post_load
  ahci: handle LIST_ON and FIS_ON in map helpers
  ahci: Do not unmap NULL addresses
  fdc: always compile-check debug prints
  ide: fix device_reset to not ignore pending AIO
  ide: Add silent DRQ cancellation
  ide: replace blk_drain_all by blk_drain
  ide: move buffered DMA cancel to core
  ide: code motion
  ide: Prohibit RESET on IDE drives

Signed-off-by: Peter Maydell <[email protected]>