media: dt-bindings: media: renesas,fcp: Add resets and iommus properties

The resets and iommus properties are used in DT sources in the kernel
tree. Document them, and make resets mandatory. The iommus property is
optional as not all platforms wire the FCP to a functional IOMMU.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>