Unify variable names(err/ret) of return values

Signed-off-by: Roger Tseng <rogerable@realtek.com>
Unify switch-case breaking using "break" instead of "goto".

Signed-off-by: Roger Tseng <rogerable@realtek.com>
Remove inappropriate debug messages.

Signed-off-by: Roger Tseng <rogerable@realtek.com>