[PATCH] I2C: move i2c-dev to use dynamic class devices

i2c-dev doesn't use the reference counting logic of struct class_device so move
it to the dynamic method.  This makes the code paths simpler and the driver
smaller.

Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Jean Delvare <khali@linux-fr.org>