i2c: Convert drivers/i2c/muxes/* to use module_i2c_driver()

This patch converts the drivers in drivers/i2c/muxes/* to use the
module_i2c_driver() macro which makes the code smaller and a bit simpler.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Wolfram Sang <w.sang@pengutronix.de>
Cc: Guenter Roeck <guenter.roeck@ericsson.com>
Cc: Michael Lawnick <ml.lawnick@gmx.de>
Cc: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Jean Delvare <khali@linux-fr.org>