perl: removes useless files in target tree

$(TARGET_DIR)/usr/lib/perl5/$(PERL_VERSION)/$(PERL_ARCHNAME)/CORE contains include files.
*.bs & .packlist files come with perl or perl/cpan packages.

Signed-off-by: Francois Perrad <francois.perrad@gadz.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>