net/socket/getsockopt.c: Eliminate warning

##[error]socket/getsockopt.c:362:7: error: 'ret' may be used uninitialized in this function [-Werror=maybe-uninitialized]
       int ret;
           ^~~

net/socket/getsockopt.c

@@ -359,7 +359,7 @@ static int psock_socketlevel_option(FAR struct socket *psock, int option,
 int psock_getsockopt(FAR struct socket *psock, int level, int option,
                      FAR void *value, FAR socklen_t *value_len)
 {
-  int ret;
+  int ret = OK;
 
   /* Verify that the sockfd corresponds to valid, allocated socket */