i2c-gpio: Add support for new-style clients

Use i2c_bit_add_numbered_bus() so that the i2c-gpio adapter works well
with new-style pre-declared devices.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Jean Delvare <khali@linux-fr.org>