Removes const qualification for two methods in TargetDataLowering.

Removes const qualifier for TargetDataLowering::lowerGlobals() and TargetDataLowering::lowerConstants()

BUG= None
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/1177873003.
diff --git a/src/IceTargetLoweringMIPS32.cpp b/src/IceTargetLoweringMIPS32.cpp
index 494f233..748881e 100644
--- a/src/IceTargetLoweringMIPS32.cpp
+++ b/src/IceTargetLoweringMIPS32.cpp
@@ -677,7 +677,7 @@
 }
 
 void TargetDataMIPS32::lowerGlobals(
-    std::unique_ptr<VariableDeclarationList> Vars) const {
+    std::unique_ptr<VariableDeclarationList> Vars) {
   switch (Ctx->getFlags().getOutFileType()) {
   case FT_Elf: {
     ELFObjectWriter *Writer = Ctx->getObjectWriter();
@@ -696,7 +696,7 @@
   }
 }
 
-void TargetDataMIPS32::lowerConstants() const {
+void TargetDataMIPS32::lowerConstants() {
   if (Ctx->getFlags().getDisableTranslation())
     return;
   llvm::report_fatal_error("Not yet implemented");