media: dt-bindings: cadence-csi2rx: Convert to DT schema

Convert DT bindings document for Cadence MIPI-CSI2 RX controller to
DT schema format.

For compatible, new compatibles should not be messed with conversion,
but the original binding did not specify any SoC-specific compatible
string, so add the StarFive compatible string.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Jack Zhu <jack.zhu@starfivetech.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>