MIPS: Fix unbounded label counter.

src/mips/assembler-mips.cc

Index: src/mips/assembler-mips.cc
diff --git a/src/mips/assembler-mips.cc b/src/mips/assembler-mips.cc
index 8e873c8f0a839b979f175a50b9566f432014637b..f4d8a68490faa8852a5c65156e18a21482f63696 100644
--- a/src/mips/assembler-mips.cc
+++ b/src/mips/assembler-mips.cc
@@ -2959,6 +2959,7 @@ void Assembler::dd(Label* label) {
     data = reinterpret_cast<uint32_t>(buffer_ + label->pos());
   } else {
     data = jump_address(label);
+    unbound_labels_count_++;
     internal_reference_positions_.insert(label->pos());
   }
   RecordRelocInfo(RelocInfo::INTERNAL_REFERENCE);