ASoC: atmel_ssc_dai: fix ssc error path

We do not have to free a resource that is not allocated yet.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: Liam Girdwood <lrg@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>