Add typecast to silence -Wswitch warning introduced by r153153.

llvm-svn: 153155
diff --git a/llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp b/llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp
index 7f5c377..9d5a2f1 100644
--- a/llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp
+++ b/llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp
@@ -99,7 +99,7 @@
     // Used to point to big endian bytes
     unsigned FullSize;
 
-    switch (Kind) {
+    switch ((unsigned)Kind) {
     case Mips::fixup_Mips_16:
       FullSize = 2;
       break;