libc/<arch>/sys/Makefile.inc: remove cruft

Remove stray blank lines left over from $FreeBSD$ removal as well as
some CVS-era (perhaps pre-repocopy) version comments.

Reviewed by: emaste
Differential Revision: https://reviews.freebsd.org/D42611

(cherry picked from commit b73eace889f1db518a7b0b3372351e0cbf550085)