i3c: fix uninitialized variable use in i2c setup

Commit 31b9887c ("i3c: remove i2c board info from i2c_dev_desc")
removed the boardinfo from i2c_dev_desc to decouple device enumeration from
setup but did not correctly lookup the i2c_dev_desc to store the new
device, instead dereferencing an uninitialized variable.

Lookup the device that has already been registered by address to store
the i2c client device.

Fixes: 31b9887c ("i3c: remove i2c board info from i2c_dev_desc")
Reported-by: kernel test robot <lkp@intel.com>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Jamie Iles <quic_jiles@quicinc.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20220308134226.1042367-1-quic_jiles@quicinc.com