drm/bridge: lvds-codec: Add support for regulator

Add the support for enabling optional regulator that may be used as VCC
source.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
[Replaced 'error' variable with 'ret']
[Renamed regulator from 'vcc' to 'power']
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200922105526.5252-1-laurent.pinchart+renesas@ideasonboard.com