drm/i915: Fix SDVO TV support

This brings SDVO TV support from 2D driver, including origin
fix f1ca56e17d0 and later fix 2fcf4fcccfe. Also fix wrong modeline
definitions for SDVO TV.

Signed-off-by: Zhenyu Wang <zhenyu.z.wang@intel.com>
Signed-off-by: Eric Anholt <eric@anholt.net>