[M68k] Fix incorrect boolean content type

M68k's SETCC instruction (`scc`) distinctly fills the destination byte
with all 1s. If boolean contents are set to `ZeroOrOneBooleanContent`,
LLVM can mistakenly think the destination holds `0x01` instead of `0xff`
and emit broken code as a result. This change corrects the boolean
content type to `ZeroOrNegativeOneBooleanContent`.

Author: dansalvato

llvm/lib/Target/M68k/M68kISelLowering.cpp

@@ -51,7 +51,7 @@ M68kTargetLowering::M68kTargetLowering(const M68kTargetMachine &TM,
 
   MVT PtrVT = MVT::i32;
 
-  setBooleanContents(ZeroOrOneBooleanContent);
+  setBooleanContents(ZeroOrNegativeOneBooleanContent);
 
   auto *RegInfo = Subtarget.getRegisterInfo();
   setStackPointerRegisterToSaveRestore(RegInfo->getStackRegister());