Simplify function timerDelta()

I believe - because we use for all operands and the result the same integer type - we can simplify the function in ldl_mac.c
```c
static uint32_t timerDelta(uint32_t timeout, uint32_t time)
{
    return (timeout <= time) ? (time - timeout) : (UINT32_MAX - timeout + time);
}
```
to
```c
static uint32_t timerDelta(uint32_t timeout, uint32_t time)
{
    return (time - timeout);
}
```