drm/bridge: Repurpose lvds-encoder.c

lvds-encoder.c implementation is also suitable for LVDS decoders,
not just LVDS encoders.
Instead of creating a new driver for addressing support for
transparent LVDS decoders, repurpose lvds-encoder.c for the greater
good with this patch.

This patch only "rebrands" the lvds-encoder.c driver, to make it
suitable for hosting LVDS decoders support. The actual support for
LVDS decoders will come with a later patch.

Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1573660292-10629-6-git-send-email-fabrizio.castro@bp.renesas.com