MIPS: Fix unbounded label counter.

src/mips64/assembler-mips64.cc

Index: src/mips64/assembler-mips64.cc
diff --git a/src/mips64/assembler-mips64.cc b/src/mips64/assembler-mips64.cc
index 420dc1874eca17d7c5b5f078f35b54b48b4d3b35..8907adf23f0a0a3fbf973057184d9992a08d78e6 100644
--- a/src/mips64/assembler-mips64.cc
+++ b/src/mips64/assembler-mips64.cc
@@ -3212,6 +3212,7 @@ void Assembler::dd(Label* label) {
     data = reinterpret_cast<uint64_t>(buffer_ + label->pos());
   } else {
     data = jump_address(label);
+    unbound_labels_count_++;
     internal_reference_positions_.insert(label->pos());
   }
   RecordRelocInfo(RelocInfo::INTERNAL_REFERENCE);