mfd: max8998 - fix incorrect kfree(i2c) in i2c_driver probe callback handler

The i2c_client received in probe() should not be kfree()'d.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>