drm: Remove crtc/connector->save/restore hooks

drm: Remove crtc/connector->save/restore hooks

They're not how system suspend/resume should be done with atomic
(there's new helpers for that developed by Thierry Reding), and for
legacy drivers this really should be a helper hook and not a core one.

But there's not even helper code to use them, and only 2 drivers
(which now have their own private hooks) set them. Ditch them.

Saves me typing some kerneldoc, too ;-)

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1449218769-16577-15-git-send-email-daniel.vetter@ffwll.ch
Reviewed-by: Thierry Reding <treding@nvidia.com>