drm/i915: Use i915 instead of dev_priv insied the file_priv structure

In the process of renaming all instances of 'dev_priv' to 'i915',
start using 'i915' within the 'drm_i915_file_private' structure.

Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230322001611.632321-1-andi.shyti@linux.intel.com

drm/i915: Explicitly track DRM clients

Tracking DRM clients more explicitly will allow later patches to
accumulate past and current GPU usage in a centralised place and also
consolidate access to owning task pid/name.

Unique client id is also assigned for the purpose of distinguishing/
consolidating between multiple file descriptors owned by the same process.

v2:
Chris Wilson:
* Enclose new members into dedicated structs.
* Protect against failed sysfs registration.

v3:
* sysfs_attr_init.

v4:
* Fix for internal clients.

v5:
* Use cyclic ida for client id. (Chris)
* Do not leak pid reference. (Chris)
* Tidy code with some locals.

v6:
* Use xa_alloc_cyclic to simplify locking. (Chris)
* No need to unregister individial sysfs files. (Chris)
* Rebase on top of fpriv kref.
* Track client closed status and reflect in sysfs.

v7:
* Make drm_client more standalone concept.

v8:
* Simplify sysfs show. (Chris)
* Always track name and pid.

v9:
* Fix cyclic id assignment.

v10:
* No need for a mutex around xa_alloc_cyclic.
* Refactor sysfs into own function.
* Unregister sysfs before freeing pid and name.
* Move clients setup into own function.

v11:
* Call clients init directly from driver init. (Chris)

v12:
* Do not fail client add on id wrap. (Maciej)

v13 (Lucas): Rebase.

v14:
* Dropped sysfs bits.

v15:
* Dropped tracking of pid/ and name.
* Dropped RCU freeing of the client object.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> # v11
Reviewed-by: Aravind Iddamsetty <aravind.iddamsetty@intel.com> # v11
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220401142205.3123159-2-tvrtko.ursulin@linux.intel.com

drm/i915: split out i915_file_private.h from i915_drv.h

Limit the scope of struct drm_i915_file_private to the files that
actually need it.

Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/e375859dc1729a1b988036e4103e5b1bd48caa00.1644507885.git.jani.nikula@intel.com