i2c: Update the list of bus IDs

* The Voodoo3 has no SMBus, it has two bit-banged busses which
  already have an ID assigned (I2C_HW_B_VOO).
* The i2c-ipmi bus driver was a non-sense, it'll never be ported
  to Linux 2.6.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Yani Ioannou <yani.ioannou@gmail.com>