Those macros are all about convenience. However, always using 64 bit makes casts
nececcary that goes against the idea of having a convenience macro.
E.g. when printing a frequency in KHZ one might want to do
printf("freq: %lu kHz\n", freq / KHZ(1));
leads to an error
> error: format '%lu' expects argument of type 'long unsigned int', but argument 2 has type 'long long unsigned int'
Now we would have to cast - `%llu` is not available with newlib-nano and wholly
uneccecary.
Only use 64 bit artithmetic where necessary (GHZ, GiB), not for smaller units.
