i2c-ocores: Can add I2C devices to the bus

There is sometimes a need for the ocores driver to add devices to the
bus when installed.

i2c_register_board_info can not always be used, because the I2C devices
 are not known at an early state, they could for instance be connected
 on a I2C bus on a PCI device which has the Open Cores IP.

i2c_new_device can not be used in all cases either since the resulting
bus nummer might be unknown.

The solution is the pass a list of I2C devices in the platform data to
the Open Cores driver. This is useful for MFD drivers.

Signed-off-by: Richard Röjfors <richard.rojfors.ext@mocean-labs.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>