Add I2C nodes for Hi3660-hikey960.

On HiKey960,
I2C0, I2C7 are connected to Low Speed Expansion Connector.
I2C1 is connected to ADV7535.
I2C3 is connected to USB5734.

Cc: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Signed-off-by: Guodong Xu <guodong.xu@linaro.org>
Signed-off-by: Wei Xu <xuwei5@hisilicon.com>