pf: renumber DIOCKEEPCOUNTERS

We accidentally had two ioctls use the same base number
(DIOCKEEPCOUNTERS and DIOCGIFSPEEDV{0,1}). We get away with that on most
platforms because the size of the argument structures is different.
This does break CHERI, and is generally a bad idea anyway.
Renumber to avoid this collision.

Reported by: jhb