i2c: fsi: Add port structures

Add and initialize I2C adapters for each port on the FSI-attached I2C
master. Ports for each master are defined in the devicetree.

Signed-off-by: Eddie James <eajames@linux.vnet.ibm.com>
Tested-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>