llvm-mc: Make MCValue take const MCSymbol*s.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@80078 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/llvm-mc/AsmExpr.cpp b/tools/llvm-mc/AsmExpr.cpp
index fbb0c53..226dd13 100644
--- a/tools/llvm-mc/AsmExpr.cpp
+++ b/tools/llvm-mc/AsmExpr.cpp
@@ -26,16 +26,16 @@
   return true;
 }
 
-static bool EvaluateSymbolicAdd(const MCValue &LHS, MCSymbol *RHS_A, 
-                                MCSymbol *RHS_B, int64_t RHS_Cst,
+static bool EvaluateSymbolicAdd(const MCValue &LHS, const MCSymbol *RHS_A, 
+                                const MCSymbol *RHS_B, int64_t RHS_Cst,
                                 MCValue &Res) {
   // We can't add or subtract two symbols.
   if ((LHS.getSymA() && RHS_A) ||
       (LHS.getSymB() && RHS_B))
     return false;
 
-  MCSymbol *A = LHS.getSymA() ? LHS.getSymA() : RHS_A;
-  MCSymbol *B = LHS.getSymB() ? LHS.getSymB() : RHS_B;
+  const MCSymbol *A = LHS.getSymA() ? LHS.getSymA() : RHS_A;
+  const MCSymbol *B = LHS.getSymB() ? LHS.getSymB() : RHS_B;
   if (B) {
     // If we have a negated symbol, then we must have also have a non-negated
     // symbol in order to encode the expression. We can do this check later to