drm: Manage drm_vblank_cleanup with drmm_

drm: Manage drm_vblank_cleanup with drmm_

Nothing special here, except that this is the first time that we
automatically clean up something that's initialized with an explicit
driver call. But the cleanup was done at the very end of the release
sequence for all drivers, and that's still the case. At least without
more uses of drmm_ through explicit driver calls.

Also for this one we need drmm_kcalloc, so lets add those.

The motivation here is to allow us to remove the explicit calls to
drm_dev_fini() from all drivers.

v2: Sort includes (Laurent)

v3: Motivate the change in the commit message better (Sam)

Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200323144950.3018436-25-daniel.vetter@ffwll.ch