i2c: fix init on generic board

On generic board, the i2c init initialize only
one bus. But the new i2c subsystem allow to
manage severals i2c bus. So in the case, instead
of initializing a bus, we just set the current
i2c bus. The initialization will be done in
the i2c command.

Signed-off-by: Philippe Reynes <tremyfr@yahoo.fr>