[AMDGPU] Revert "[AMDGPU] Add options for waitcnt pass debugging; add instr count...

[AMDGPU] Revert "[AMDGPU] Add options for waitcnt pass debugging; add instr count in debug output."

Patch caused a buildbot failure; http://lab.llvm.org:8011/builders/lld-x86_64-darwin13/builds/15733/steps/build_Lld/logs/stdio :
lib/Target/AMDGPU/SIInsertWaitcnts.cpp:396:11: error: private field 'InstCnt' is not used [-Werror,-Wunused-private-field]
  int32_t InstCnt = 0;
          ^
1 error generated.
"
This reverts commit 71627f79010aafe74fdcba901bba28dd7caa0869.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@320086 91177308-0d34-0410-b5e6-96231b3b80d8