stop building arm LINT-V5 kernel

r354290 removed arm.arm from universe, but arm.arm kernels were still
found and built during the kernel stage. r354934 tagged armv5 kernel
configs as NO_UNIVERSE, but LINT-V5 remained. Stop building it as well.
Leave the clean rule in place for now so folks don't end up with a stale
LINT-V5.

Reviewed by: imp
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D22560