drm/i915: Remove unused members from intel_tv.c

They have been unused since 2010, after the code for
intel_tv_save/restore was removed in the below commit:

commit 6443170f
Author: Eric Anholt <eric@anholt.net>
Date:   Fri Apr 2 15:24:27 2010 -0700

    drm/i915: Remove dead KMS encoder save/restore code.

    This was brought over from UMS, and used for a while until we decided
    that drm_helper_resume_force_mode was easier and more reliable, since
    it didn't require duplicating all the code deleted here.  We just
    forgot to delete all that junk for a while.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1491815239-10685-2-git-send-email-maarten.lankhorst@linux.intel.com
[mlankhorst: Add commit blurb based on danvet's feedback.]