Add bindings documentation for Xilinx MIPI CSI-2 Rx Subsystem.

The Xilinx MIPI CSI-2 Rx Subsystem consists of a CSI-2 Rx controller, a
D-PHY in Rx mode and a Video Format Bridge.

[Fix indentation error in if...then...else]
[Fix number of cells in reg property]
Signed-off-by: Vishal Sagar <vishal.sagar@xilinx.com>
Reviewed-by: Hyun Kwon <hyun.kwon@xilinx.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Luca Ceresoli <luca@lucaceresoli.net>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>