The current implementation accesses the `child` fwnode handle outside of
device_for_each_child_node() without incrementing its refcount.

Add the missing call to `fwnode_handle_get(child)`.

The cleanup process where `child` is accessed is not right either
because a single call to `fwnode_handle_put()` is carried out in case of
an error, ignoring unasigned nodes at the point when the error happens.

Keep `child` inside of the first loop, and use the helper pointer that
receives references via `fwnode_handle_get()` to handle the child nodes
within the second loop. Keeping `child` inside the first node has also
the advantage that the scoped version of the loop can be used.

Fixes: ee4e80b2 ("leds: pca995x: Add support for PCA995X chips")
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Link: https://lore.kernel.org/r/20240807-leds-pca995x-fix-fwnode-usage-v1-1-8057c84dc583@gmail.comSigned-off-by: Lee Jones <lee@kernel.org>