ASoC: Ux500: Dispose of device nodes correctly

When of_parse_phandle() is used to find a device node, its
reference count is incremented by the helper. Once we're
finished with them, it's our responsibly to ensure they
are freed in the correct manor.

Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>