selinux, kbuild: remove unnecessary $(hostprogs-y) from clean-files

Files added to hostprogs-y are cleaned. (See scripts/Makefile.clean)
Adding them to clean-files is redundant.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Acked-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Paul Moore <pmoore@redhat.com>