Add ARM TARGET2 relocation. The testcase will follow with actualy use-case.
Based on the patch by Logan Chien!

llvm-svn: 167633
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
index b53da3b..99e4f71 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
@@ -246,6 +246,9 @@
       case MCSymbolRefExpr::VK_ARM_TARGET1:
         Type = ELF::R_ARM_TARGET1;
         break;
+      case MCSymbolRefExpr::VK_ARM_TARGET2:
+        Type = ELF::R_ARM_TARGET2;
+        break;
       } 
       break;
     case ARM::fixup_arm_ldst_pcrel_12: