Remove unused DisableRedZone option.

Patch by Steve King.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221282 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/CommandFlags.h

@@ -92,11 +92,6 @@ FileType("filetype", cl::init(TargetMachine::CGFT_AssemblyFile),
                         "Emit nothing, for performance testing"),
              clEnumValEnd));
 
-cl::opt<bool>
-DisableRedZone("disable-red-zone",
-               cl::desc("Do not emit code that uses the red zone."),
-               cl::init(false));
-
 cl::opt<bool>
 EnableFPMAD("enable-fp-mad",
             cl::desc("Enable less precise MAD instructions to be generated"),