procdesc: Remove dead code

[markj]

Summary

As far as I can see, it is impossible for procdesc_exit() to observe
pd->pd_fpcount == 0: if procdesc_close() decrements that counter to
zero, then it will clean up the procdesc structure too, and this is
atomic with respect to the proctree lock.

No functional change intended.

[kib]

sys/kern/sys_procdesc.c

281

Can we please lave the bool return type for now? It conflicts with the p_zombieref patch.

[markj]

sys/kern/sys_procdesc.c

281

I will just not commit this until your patch lands.

[kib]

sys/kern/sys_procdesc.c

281

In fact, no need, this was over-reaction. Please go ahead.