drm/i915/tv: fix gen4 composite s-video tv-out

drm/i915/tv: fix gen4 composite s-video tv-out

commit e1f23f3dd817f53f622e486913ac662add46eeed upstream.

This is *not* bisected, but the likely regression is

commit c35614380d5c956bfda20eab2755b2f5a7d6f1e7
Author: Zhao Yakui <yakui.zhao@intel.com>
Date:   Tue Nov 24 09:48:48 2009 +0800

    drm/i915: Don't set up the TV port if it isn't in the BIOS table.

The commit does not check for all TV device types that might be present
in the VBT, disabling TV out for the missing ones. Add composite
S-video.

Reported-and-tested-by: Matthew Khouzam <matthew.khouzam@gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=73362
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
[bwh: Backported to 3.2: s/old\.device_type/device_type/]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>