Limit CFI blacklist entries to specific CFI mode
Since D37924 and D37925 were merged, it's now possible to specify
individual sanitizers or CFI modes in sanitizer blacklists. Update the
CFI blacklist entries to only apply to cfi-unrelated-cast checks.
Reviewers: eugenis, pcc
Reviewed By: eugenis
Differential Revision: https://reviews.llvm.org/D38385