leds: bd2606mvv: Fix device child node usage in bd2606mvv_probe()

leds: bd2606mvv: Fix device child node usage in bd2606mvv_probe()

The current implementation accesses the `child` fwnode handle outside of
fwnode_for_each_available_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.

Moreover, the iterated nodes are direct children of the device node,
and the `device_for_each_child_node()` macro accounts for child node
availability. By restricting `child` to live within that loop, the
scoped version of it can be used to simplify the error handling.

`fwnode_for_each_available_child_node()` is meant to access the child
nodes of an fwnode, and therefore not direct child nodes of the device
node.

Use `device_for_each_child_node_scoped()` to indicate device's direct
child nodes.

Fixes: 8325642d2757 ("leds: bd2606mvv: Driver for the Rohm 6 Channel i2c LED driver")
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Link: https://lore.kernel.org/r/20240721-device_for_each_child_node-available-v2-3-f33748fd8b2d@gmail.com
Signed-off-by: Lee Jones <lee@kernel.org>