ASoC: fsl: Fix error handling if platform_device_add fails

Call platform_device_put() instead of platform_device_unregister() if
platform_device_add() fails.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Liam Girdwood <lrg@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>