drm: Convert connector_helper_funcs->atomic_check to accept drm_atomic_state

Everyone who implements connector_helper_funcs->atomic_check reaches
into the connector state to get the atomic state. Instead of continuing
this pattern, change the callback signature to just give atomic state
and let the driver determine what it does and does not need from it.

Eventually all atomic functions should do this, but that's just too much
busy work for me.

Changes in v3:
- Added to the set
Changes in v4:
- None
Changes in v5:
- intel_digital_connector_atomic_check declaration moved to i915_atomic.h

Link to v3: https://patchwork.freedesktop.org/patch/msgid/[email protected]
Link to v4: https://patchwork.freedesktop.org/patch/msgid/[email protected]

Cc: Daniel Vetter <[email protected]>
Cc: Ville Syrjälä <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
Cc: Rodrigo Vivi <[email protected]>
Cc: Ben Skeggs <[email protected]>
Cc: Laurent Pinchart <[email protected]>
Cc: Kieran Bingham <[email protected]>
Cc: Eric Anholt <[email protected]>
Tested-by: Heiko Stuebner <[email protected]>
Reviewed-by: Laurent Pinchart <[email protected]> [for rcar lvds]
Acked-by: Daniel Vetter <[email protected]>
Signed-off-by: Sean Paul <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

include/drm/drm_modeset_helper_vtables.h

@@ -1028,7 +1028,7 @@ struct drm_connector_helper_funcs {
 	 * deadlock.
 	 */
 	int (*atomic_check)(struct drm_connector *connector,
-			    struct drm_connector_state *state);
+			    struct drm_atomic_state *state);
 
 	/**
 	 * @atomic_commit: