i2c: i2c-cadence: Initialize configuration before probing devices

The cadence I2C driver calls cdns_i2c_writereg(..) to setup a workaround
in the controller, but did so after calling i2c_add_adapter() which starts
probing devices on the bus. Change the order so that the configuration is
completely finished before using the adapter.

Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>