powerpc/windfarm: Use module_i2c_driver to simplify the code

Use the module_i2c_driver() macro to make the code smaller
and a bit simpler.

dpatch engine is used to auto generate this patch.
(https://github.com/weiyj/dpatch)

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>