drm/bridge: display-connector: handle hdmi-pwr supply

On some devices the +5V Power pin of the HDMI connector and/or the ESD
protection logic is powered on by a separate regulator. Instead of
declaring this regulator as always-on, make hdmi-connector support the
additional hdmi-pwr supply.

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/20230531000259.3758235-4-dmitry.baryshkov@linaro.org