ASoC: pxa: fix a memory leak in probe()

Free the "priv" pointer before returning the error code.

Fixes: 90eb6b59

 ("ASoC: pxa-ssp: add support for an external clock in devicetree")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/r/84ac2313-1420-471a-b2cb-3269a2e12a7c@moroto.mountain
Signed-off-by: Mark Brown <broonie@kernel.org>