drm/i915/selftests: make mock_drm.h self-contained

Needs i915_drv.h because i915 gets dereferenced.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191219155652.2666-2-jani.nikula@intel.com

drm/i915/selftests: Complete transition to a real struct file mock

Since drm provided us with a real struct file we can use for our
anonymous internal clients (mock_file), complete our transition to using
that as the primary interface (and not the mocked up struct drm_file we
previous were using).

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191107213929.23286-1-chris@chris-wilson.co.uk

drm/i915/selftests: Replace mock_file hackery with drm's true fake

As drm now exports a method to create an anonymous struct file around a
drm_device for internal use, make use of it to avoid our horrible hacks.

Danial suggested that the mock_file_put() wrapper was suitable for
drm-core, along with the mock_drm_getfile() [and that the vestigal
mock_drm_file() in this patch should perhaps be the drm interface
itself]. However, the eventual goal is to remove the mock_drm_file() and
use the struct file and fput() directly, in this patch we take a simple
transition in that direction.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20191107180601.30815-3-chris@chris-wilson.co.uk

drm/i915: Mock the GEM device for self-testing

A simulacrum of drm_i915_private to let us pretend interactions with the
device.

v2: Tidy init error paths

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170213171558.20942-6-chris@chris-wilson.co.uk