i2c/busses: Use module_platform_driver()

Convert the drivers in drivers/i2c/busses/* to use the
module_platform_driver() macro which makes the code smaller and a bit
simpler.

Cc: Ben Dooks <ben-linux@fluff.org>
Acked-by: Jochen Friedrich <jochen@scram.de>
Acked-by: Peter Korsgaard <jacmet@sunsite.dk>
Acked-by: Wolfram Sang <w.sang@pengutronix.de>
Cc: Manuel Lauss <manuel.lauss@googlemail.com>
Cc: Barry Song <21cnbao@gmail.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Yong Zhang <yong.zhang0@gmail.com>
Cc: Lucas De Marchi <lucas.demarchi@profusion.mobi>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>