Input: adp5589-keys - use devm_kzalloc() to allocate the kpad object

This removes the need to manually free the kpad object and cleans up some
exit/error paths.  The error path cleanup should reduce the risk of any
memory leaks with this object.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20201112074308.71351-2-alexandru.ardelean@analog.com


Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>