i2c: New i2c-tiny-usb bus driver

Add a driver for the i2c-tiny-usb interface. This is a simple
do-it-yourself USB to I2C interface targeted at experimental and
home use. See the i2c-tiny-usb homepage for hardware details:
http://www.harbaum.org/till/i2c_tiny_usb



Signed-off-by: Till Harbaum <till@harbaum.org>
Signed-off-by: Jean Delvare <khali@linux-fr.org>