drm/bridge: anx7625: Add anx7625 MIPI DSI/DPI to DP

The ANX7625 is an ultra-low power 4K Mobile HD Transmitter designed
for portable device. It converts MIPI DSI/DPI to DisplayPort 1.3 4K.

Signed-off-by: Xin Ji <xji@analogixsemi.com>
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/528b76c1a4f7b6ea85371bfae4bde389aec4bb24.1600423932.git.xji@analogixsemi.com