dt-bindings: media: Add DT bindings for TI CSI2RX driver

TI's J721E uses the Cadence CSI2RX and DPHY peripherals to facilitate
capture over a CSI-2 bus. The TI CSI2RX platform driver glues all the
parts together.

Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>