drm/bridge: display-connector: rename dp_pwr to connector_pwr

In preparation to adding support for the hdmi_pwr supply, rename dp_pwr
structure field to the generic connector_pwr.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230531000259.3758235-3-dmitry.baryshkov@linaro.org