media: dt-bindings: ov5640: refine CSI-2 and add parallel interface

Refine CSI-2 endpoint documentation and add bindings
for DVP parallel interface support.

Signed-off-by: Hugues Fruchet <hugues.fruchet@st.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>