drm: Define DRM_MODE_CONNECTOR_TV

The existing TV connector types are often unsuitable either because
there is no way to probe them until they're actually plugged in or
because they can change during run time (e.g. 7-pin DIN connectors
that behave as S-Video, Component, Composite or SCART depending on the
adaptor plugged in).

Signed-off-by: Francisco Jerez <currojerez@riseup.net>
Signed-off-by: Dave Airlie <airlied@redhat.com>