i2c: Kill struct i2c_device_id

I2C devices do not have any form of ID as PCI or USB devices have.
No driver uses "MODULE_DEVICE_TABLE(i2c, ...)" because it doesn't
make sense. So we can get rid of struct i2c_device_id and the
associated support code.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: Greg KH <greg@kroah.com>