[llvm] [TTI] Use Register in isLoadFromStackSlot and isStoreToStackSlot [nfc] (PR #80339)

[Jay Foad via llvm-commits]

================
@@ -269,7 +269,7 @@ class TargetInstrInfo : public MCInstrInfo {
   /// the destination along with the FrameIndex of the loaded stack slot.  If
   /// not, return 0.  This predicate must return 0 if the instruction has
----------------
jayfoad wrote:

Nit: update this (and other) comment to say `NoRegister` instead of `0`? Also maybe "return the ... register" instead of "return the ... register number"?

https://github.com/llvm/llvm-project/pull/80339