simplify the mdev interface v6

[Christoph Hellwig <hch@lst.de>]

Hi all,

this series signigicantly simplies the mdev driver interface by following
the patterns for device model interaction used elsewhere in the kernel.

Changes since v5:
 - rebased to the latest vfio/next branch
 - drop the last patch again
 - make sure show_available_instances works properly for the internallly
   tracked case

Changes since v4:
 - move the kobject_put later in mdev_device_release 
 - add a Fixes tag for the first patch
 - add another patch to remove an extra kobject_get/put

Changes since v3:
 - make the sysfs_name and pretty_name fields pointers instead of arrays
 - add an i915 cleanup to prepare for the above

Changes since v2:
 - rebased to vfio/next
 - fix a pre-existing memory leak in i915 instead of making it worse
 - never manipulate if ->available_instances if drv->get_available is
   provided
 - keep a parent reference for the mdev_type
 - keep a few of the sysfs.c helper function around
 - improve the documentation for the parent device lifetime
 - minor spellig / formatting fixes

Changes since v1:
 - embedd the mdev_parent into a different sub-structure in i916
 - remove headers now inclued by mdev.h from individual source files
 - pass an array of mdev_types to mdev_register_parent
 - add additional patches to implement all attributes on the
   mdev_type in the core code

Diffstat:
 Documentation/driver-api/vfio-mediated-device.rst |   26 +-
 Documentation/s390/vfio-ap.rst                    |    2 
 Documentation/s390/vfio-ccw.rst                   |    2 
 drivers/gpu/drm/i915/gvt/aperture_gm.c            |   20 +-
 drivers/gpu/drm/i915/gvt/gvt.h                    |   42 ++--
 drivers/gpu/drm/i915/gvt/kvmgt.c                  |  168 ++++-------------
 drivers/gpu/drm/i915/gvt/vgpu.c                   |  210 +++++++---------------
 drivers/s390/cio/cio.h                            |    4 
 drivers/s390/cio/vfio_ccw_drv.c                   |   12 -
 drivers/s390/cio/vfio_ccw_ops.c                   |   51 -----
 drivers/s390/cio/vfio_ccw_private.h               |    2 
 drivers/s390/crypto/vfio_ap_ops.c                 |   68 +------
 drivers/s390/crypto/vfio_ap_private.h             |    6 
 drivers/vfio/mdev/mdev_core.c                     |  190 ++++---------------
 drivers/vfio/mdev/mdev_driver.c                   |    7 
 drivers/vfio/mdev/mdev_private.h                  |   32 ---
 drivers/vfio/mdev/mdev_sysfs.c                    |  189 ++++++++++---------
 include/linux/mdev.h                              |   77 ++++----
 samples/vfio-mdev/mbochs.c                        |  103 +++-------
 samples/vfio-mdev/mdpy.c                          |  115 +++---------
 samples/vfio-mdev/mtty.c                          |   94 +++------
 21 files changed, 463 insertions(+), 957 deletions(-)