bpf: Allow creating all program types without privilege

This doesn't let you *run* the programs except in test mode, so it should
be safe.  Famous last words.

This assumes that the check-privilege-to-call-privileged-functions
patch actually catches all the cases and that there's nothing else
that should need privilege lurking in the type-specific verifiers.

Signed-off-by: Andy Lutomirski <luto@kernel.org>