drm/bridge: anx7625: add MIPI DPI input feature

The basic anx7625 driver only support MIPI DSI rx signal input.
This patch add MIPI DPI rx input configuration support, after apply
this patch, the driver can support DSI rx or DPI rx by adding
'bus-type' in DT.

Reviewed-by: Robert Foss <robert.foss@linaro.org>
Signed-off-by: Xin Ji <xji@analogixsemi.com>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20211104033639.2634502-1-xji@analogixsemi.com