ASoC: twl4030: fix child-node lookup

Fix child-node lookup during probe, which ended up searching the whole
device tree depth-first starting at the parent rather than just matching
on its children.

To make things worse, the parent codec node was also prematurely freed,
while the child node was leaked.

Fixes: 2d6d649a ("ASoC: twl4030: Support for DT booted kernel")
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable <stable@vger.kernel.org>