asoc: codecs: Fix NULL pointer dereference in wcd9xxx slim probe

When slim device is NULL or pdata allocation fails in wcd9xxx
slim probe, devm_kfree uses slim device leading to a NULL pointer
dereference. Fix this by returning from probe in these scenarios.

Change-Id: I232661d8ba0320469bc4486e7dd82713e9b53d73
Signed-off-by: Aditya Bavanari <abavanar@codeaurora.org>