ASoC: use int type to store negative error codes

Merge series from Qianfeng Rong <rongqianfeng@vivo.com>:

The 'ret' variable usually is used to store returns from some functions,
which return either zero on success or negative error codes on failure.

Storing the negative error codes in unsigned type, doesn't cause an issue
at runtime but it's ugly as pants.  Additionally, assigning negative error
codes to unsigned type may trigger a GCC warning when the -Wsign-conversion
flag is enabled.

Change "ret" from u32/unsigned int to int type.  No effect on runtime.