dt-bindings: i2c: dw: cancel mandatory requirements for "#address-cells" and "#size-cells"

The "#address-cells" and "#size-cells" are required only when the I2C
controller has subnodes. However, some I2C controllers defined in
"arch/arm64/boot/dts/amd/" and "arch/arm64/boot/dts/hisilicon/"
directories do not have child nodes. So they don't need these two
properties and don't write them explicitly.

Therefore, setting properties "#address-cells" and "#size-cells" as
"required" in this yaml file causes the following warnings:
/root/linux-next/arch/arm64/boot/dts/hisilicon/hi6220-hikey.dt.yaml: \
i2c@f7100000: '#address-cells' is a required property
/root/linux-next/arch/arm64/boot/dts/hisilicon/hi6220-hikey.dt.yaml: \
i2c@f7100000: '#size-cells' is a required property

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Link: https://lore.kernel.org/r/20201214124347.2120-2-thunder.leizhen@huawei.com


Signed-off-by: Rob Herring <robh@kernel.org>