dt-bindings: i2c: brcm,iproc-i2c: convert to the json-schema

This helps validating DTS files.

Introduced changes:
1. Added arm-gic.h include

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Link: https://lore.kernel.org/r/20210713093155.1752-1-zajec5@gmail.com
Signed-off-by: Rob Herring <robh@kernel.org>