mfd: Avoid calling platform_device_put() twice in ucb1400 probe error path

In the case of goto err2, what we want is to call
platform_device_del() instead of platform_device_unregister().
Otherwise, we call platform_device_put() twice.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>