mfd: 88pm860x: Drop devm_kfree of devm_kzalloc'd data

devm_kfree() allocates memory that is released when a driver detaches.
Thus, there is no reason to explicitly call devm_kfree() in probe or remove
functions.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>