[media] Documentation: dt: Add binding documentation for S5C73M3 camera

This adds DT binding documentation for Samsung S5C73M3 camera sensor
with an embedded ISP.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>