Ugly workaround for clang 15 warning in if_alc.c

[dim]

Summary

Clang 15 warns:

sys/dev/alc/if_alc.c:3441:6: error: variable 'prog' set but not used [-Werror,-Wunused-but-set-variable]
        int prog;
            ^

I understand why it warns, since indeed the whole 'prog' variable is
never really *used* for anything, except incrementing it. So why is it
ther at all?

Can somebody who understands this code figure out what is sensible here?
To just start this review, I commented out all uses of 'prog' but that
could hardly be what the original author intended. It seems the while
loop only cares about 'cons' and 'prod', and if that is enough, the
whole 'prog' variable can be ditched?

[kib]

I suspect the code for txeof was somehow copied from rxintr and then rewritten. The prog variable there is definitely not needed, consider the fact that it is incremented twice in the normal loop flow as an additional evidence.