Wrong attribute. LLVM_ATTRIBUTE_UNUSED not LLVM_ATTRIBUTE_USED

This original fix for the build break was correct.  LLVM_ATTRIBUTE_USED
removes the warning message because it keeps the function in the object
file.  LLVM_ATTRIBUTE_UNUSED indicates that it may or may not be used
depending on build settings.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219846 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/Hexagon/InstPrinter/HexagonInstPrinter.cpp

@@ -63,7 +63,7 @@ static bool isExtended(uint64_t TSFlags) {
 }
 
 // Currently just used in an assert statement
-static bool isExtendable(uint64_t TSFlags) LLVM_ATTRIBUTE_USED;
+static bool isExtendable(uint64_t TSFlags) LLVM_ATTRIBUTE_UNUSED;
 // Return true if the instruction may be extended based on the operand value.
 static bool isExtendable(uint64_t TSFlags) {
   return (TSFlags >> HexagonII::ExtendablePos) & HexagonII::ExtendableMask;