asoc: codecs: Fix out of bounds access in register show functions

In register show functions, when snprintf returns a negative value
out of bounds access occurs while copying the data to user.
Add return value check on snprintf before copy_to_user
to fix this.

Change-Id: I1eb793721c653bf6d1fbd10f4cea3436ffe6f519
Signed-off-by: Aditya Bavanari <abavanar@codeaurora.org>