ASoC: Fix incorrect kfree in ad193x_probe error path

We allocated memory for ad193x in ad193x_spi_probe,
and will free the memory in either ad193x_spi_probe error path or
ad193x_spi_remove.

Thus we should not call kfree(ad193x) in ad193x_probe, otherwise
we have double free of ad193x.

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