ASoC: pxa: pxa-ssp: small leak in probe()

There is a small memory leak if probe() fails.

Fixes: 2023c90c ('ASoC: pxa: pxa-ssp: add DT bindings')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Mark Brown <broonie@linaro.org>