ASoC: Fix incorrect kfree in ad1836_probe error path

We allocated memory for ad1836 in ad1836_spi_probe,
and will free the memory in either ad1836_spi_probe error path or
ad1836_spi_remove.

Thus we should not call kfree(ad1836) in ad1836_probe, otherwise
we have double free of ad1836.

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>