Avoid report_fatal_error in ARM's PrintAsmOperand method.

The standard error handling in AsmPrinter::EmitInlineAsm handles this much
better, so just use it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122100 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/ARM/ARMAsmPrinter.cpp

@@ -286,7 +286,7 @@ bool ARMAsmPrinter::PrintAsmOperand(const MachineInstr *MI, unsigned OpNum,
     case 'Q':
     case 'R':
     case 'H':
-      report_fatal_error("llvm does not support 'Q', 'R', and 'H' modifiers!");
+      // These modifiers are not yet supported.
       return true;
     }
   }