drm: Make the connector .detect() callback optional

Many drivers (21 to be exact) create connectors that are always
connected (for instance to an LVDS or DSI panel). Instead of forcing
them to implement a dummy .detect() handler, make the callback optional
and consider the connector as always connected in that case.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Jyri Sarha <jsarha@ti.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Vincent Abriou <vincent.abriou@st.com>
Acked-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
[seanpaul fixed small conflict in rcar-du/rcar_du_lvdscon.c]
Signed-off-by: Sean Paul <seanpaul@chromium.org>

drivers/gpu/drm/cirrus/cirrus_mode.c

@@ -498,12 +498,6 @@ static struct drm_encoder *cirrus_connector_best_encoder(struct drm_connector
 	return NULL;
 }
 
-static enum drm_connector_status cirrus_vga_detect(struct drm_connector
-						   *connector, bool force)
-{
-	return connector_status_connected;
-}
-
 static void cirrus_connector_destroy(struct drm_connector *connector)
 {
 	drm_connector_cleanup(connector);
@@ -517,7 +511,6 @@ static const struct drm_connector_helper_funcs cirrus_vga_connector_helper_funcs
 
 static const struct drm_connector_funcs cirrus_vga_connector_funcs = {
 	.dpms = drm_helper_connector_dpms,
-	.detect = cirrus_vga_detect,
 	.fill_modes = drm_helper_probe_single_connector_modes,
 	.destroy = cirrus_connector_destroy,
 };