i2c-ibm_iic: Enable driver for all PPC4xx variants in arch/powerpc

Enable the IBM I2C driver for all PPC4xx variants by adding
"ibm,iic" to the compatible list. This way all currently available
arch/powerpc 4xx ports can make use of this driver without any changes.
Additionally all "other" compatible entries are removed since they are
not needed anymore.

Currently all 4xx PPC's have the same compatible I2C macro. If at some
time an incompatibility is detected we can take care of this with an
additional property.

Signed-off-by: Stefan Roese <sr@denx.de>
Acked-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>