[AVR] Remove a few very old TODOs that don't have enough context to understand

llvm-svn: 307622
diff --git a/llvm/lib/Target/AVR/AVRAsmPrinter.cpp b/llvm/lib/Target/AVR/AVRAsmPrinter.cpp
index f0c7b11..c058c9e 100644
--- a/llvm/lib/Target/AVR/AVRAsmPrinter.cpp
+++ b/llvm/lib/Target/AVR/AVRAsmPrinter.cpp
@@ -149,7 +149,10 @@
   (void)MO;
   assert(MO.isReg() && "Unexpected inline asm memory operand");
 
-  // TODO: We can look up the alternative name for the register if it's given.
+  // TODO: We should be able to look up the alternative name for
+  // the register if it's given.
+  // TableGen doesn't expose a way of getting retrieving names
+  // for registers.
   if (MI->getOperand(OpNum).getReg() == AVR::R31R30) {
     O << "Z";
   } else {