[MC] Rename TLSCALL as it's not ARM specific.

`MCSymbolRefExpr` variant kind for TLSCALL is prefixed with 
_ARM_ since this is how it was originally implemented.
The X86_64 version is exactly the same so there's no reason
to create a new variant, we can just rename the existing
one to be machine-independent.
This generalization is the first step to implement support
for GNU2 TLS dialect in MC.

Differential Revision:  http://reviews.llvm.org/D18160

llvm-svn: 263515
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
index 9001ad3..18d2aa6 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
@@ -109,7 +109,7 @@
       case MCSymbolRefExpr::VK_PLT:
         Type = ELF::R_ARM_CALL;
         break;
-      case MCSymbolRefExpr::VK_ARM_TLSCALL:
+      case MCSymbolRefExpr::VK_TLSCALL:
         Type = ELF::R_ARM_TLS_CALL;
         break;
       default:
@@ -141,7 +141,7 @@
     case ARM::fixup_arm_thumb_bl:
     case ARM::fixup_arm_thumb_blx:
       switch (Modifier) {
-      case MCSymbolRefExpr::VK_ARM_TLSCALL:
+      case MCSymbolRefExpr::VK_TLSCALL:
         Type = ELF::R_ARM_THM_TLS_CALL;
         break;
       default:
@@ -213,7 +213,7 @@
       case MCSymbolRefExpr::VK_ARM_TLSLDO:
         Type = ELF::R_ARM_TLS_LDO32;
         break;
-      case MCSymbolRefExpr::VK_ARM_TLSCALL:
+      case MCSymbolRefExpr::VK_TLSCALL:
         Type = ELF::R_ARM_TLS_CALL;
         break;
       case MCSymbolRefExpr::VK_ARM_TLSDESC: