dt-bindings: i2c: brcm,bcm2835-i2c: convert to YAML schema

Switch the DT binding to a YAML schema to enable the DT validation.

Signed-off-by: David Heidelberg <david@ixit.cz>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Tested-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>