clang-format: Restrict r272537 to function ref qualifiers.

Seems this isn't generally desirable.

Before:
  int const * a;

After:
  int const* a;

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@272548 91177308-0d34-0410-b5e6-96231b3b80d8