Fix some warnings from Clang in release builds:

lib/CodeGen/RegAllocGreedy.cpp:1176:18: warning: unused variable 'B' [-Wunused-variable]
    if (unsigned B = Cand.getBundles(BundleCand, BestCand)) {
                 ^
lib/CodeGen/RegAllocGreedy.cpp:1188:18: warning: unused variable 'B' [-Wunused-variable]
    if (unsigned B = Cand.getBundles(BundleCand, 0)) {
                 ^

llvm-svn: 136831