dt-bindings: i2c: brcm,kona-i2c: convert to YAML

Changes during conversion:
- add used, but previously undocumented SoC-specific compatibles
- drop references to SoCs that are not upstream
- add supported clock frequencies

Signed-off-by: Stanislav Jakubek <stano.jakubek@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Wolfram Sang <wsa@kernel.org>