Input: convert I2C drivers to use module_i2c_driver()

This patch converts the drivers in drivers/input/* 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>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>