drm/i915/tv: Fix >1024 modes on gen3

drm/i915/tv: Fix >1024 modes on gen3

On gen3 we must disable the TV encoder vertical filter for >1024
pixel wide sources. Once that's done all we can is try to center
the image on the screen. Naturally the TV mode vertical resolution
must be equal or larger than the user mode vertical resolution
or else we'd have to cut off part of the user mode.

And while we may not be able to respect the user's choice of
top and bottom borders exactly (or we'd have to reject he mode
most likely), we can try to maintain the relative sizes of the
top and bottom border with respect to each orher.

Additionally we must configure the pipe as interlaced if the
TV mode is interlaced.

v2: Make +intel_tv_connector_duplicate_state() static and drop
    the badly copy pasted kerneldoc
    s/IS_GEN3(dev_priv/IS_GEN(dev_priv, 3)/

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181112170000.27531-16-ville.syrjala@linux.intel.com
Reviewed-by: Imre Deak <imre.deak@intel.com>