drm: Add TV connector states to drm_connector_state

Some generic TV connector properties are exposed in drm_mode_config, but
they are currently handled independently in each DRM encoder driver.

Extend the drm_connector_state to store TV related states, and modify the
drm_atomic_connector_{set,get}_property() helpers to fill the connector
state accordingly.

Each driver is then responsible for checking and applying the new config
in its ->atomic_mode_{check,set}() operations.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Eric Anholt <eric@anholt.net>