Fix c++11 narrowing

The best fix for these narrowing
violations is to use static casting

As an example, this change would the following for libnaio:
error: non-constant-expression cannot be narrowed from
type 'uint32_t' (aka 'unsigned int') to 'long' in initializer list

const struct timespec req = {0, ns};
                                ^~

Change-Id: I04ed1de4497dc19772194afef3ebf8fe0c8b82bc