drm: bridge: dw-hdmi: Store current connector in struct dw_hdmi

Store the connector that the bridge is currently wired to in the dw_hdmi
structure. This is currently identical to the connector field, but will
differ once the driver supports disabling connector creation.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200526011505.31884-21-laurent.pinchart+renesas@ideasonboard.com