media: i2c: adp1653: don't reuse the same node pointer

The child device_node pointer was used for two different children.
This confused smatch, causing this warning:

drivers/media/i2c/adp1653.c:444 adp1653_of_init() warn: missing unwind goto?

Use two different pointers, one for each child node, and add separate
goto labels for each node as well. This also improves error logging
since it will now state for which node the property was missing.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
[hverkuil: fix typo: childs -> children]