mfd: Cleanup pcf50633_probe error handling

Currently the child devices were not freed if the irq could not be requested.
This patch restructures the function, that in case of an error all previously
allocated resources are freed.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>