Update libata core layer to use devres.

* ata_device_add() acquires all resources in managed mode.

* ata_host is allocated as devres associated with ata_host_release.

* Port attached status is handled as devres associated with
  ata_host_attach_release().

* Initialization failure and host removal is handedl by releasing
  devres group.

* Except for ata_scsi_release() removal, LLD interface remains the
  same.  Some functions use hacky is_managed test to support both
  managed and unmanaged devices.  These will go away once all LLDs are
  updated to use devres.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>