Revert "blockfreq: Temporarily turn on -debug-only=block-freq"

This reverts commit r206705, as planned.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206706 91177308-0d34-0410-b5e6-96231b3b80d8
Revert "blockfreq: Rewrite BlockFrequencyInfoImpl"

This reverts commit r206704, as expected.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206707 91177308-0d34-0410-b5e6-96231b3b80d8