drm: bridge: adv7511: Implement bridge connector operations

Implement the bridge connector-related .get_edid(), .detect() and
.hpd_notify() operations, and report the related bridge capabilities.

Output status detection is implemented using the same backend as for the
DRM connector, but requires making mode retrieval at detection time
optional as no pointer to the connector is available to the bridge
.detect() operation. The reason for the need to retrieve modes at
detection time is unclear to me, and this may benefit from further
refactoring of hot plug handling code.

Hot plug detection is notified through the bridge HPD notification
framework when the bridge is used without creating a connector, and
falls back to the existing implementation otherwise. CEC handling of
disconnection is handled in the new .hpd_notify() operation in the new
code path.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200526011505.31884-4-laurent.pinchart+renesas@ideasonboard.com