[CGProfile] Don't fetch BFI without profile (NFCI)

Don't fetch BFI if the function has no entry count. Peculiarly,
the implementation was already doing this for the (no longer
existing) legacy PM implementation, but the same principle applies
to the new pass manager. The only reason why the new PM doesn't
have LazyBFI is that with the new pass manager all passes are
lazy.

This improves compile-time for non-PGO builds.