dt-bindings: i2c: i2c-rk3x: Add rk3576 compatible

Just like RK356x and RK3588, RK3576 is compatible to the existing
rk3399 binding.

Signed-off-by: Detlev Casanova <detlev.casanova@collabora.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Andi Shyti <andi.shyti@kernel.org>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>