video: bridge: add basic support for the Parade DP501 transmitter

The Parade DP501 is a DP & DVI/HDMI dual-mode transmitter. It
enables an RGB/Parallel SOC output to be converted, packed and
serialized into either DP or TMDS output device. Only DisplayPort
functionality of this transmitter has been implemented and tested.

Signed-off-by: Jonas Schwöbel <jonasschwoebel@yahoo.de>
Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>