LDDRdPtrQ was marked as `earlyclobber`, which doesn't play well with
GreedyRA (which can generate this instruction through `loadRegFromStackSlot()`).
This seems to be the same case as:
a99b912c9b/llvm/lib/Target/AVR/AVRInstrInfo.td (L1421)
Closes https://github.com/llvm/llvm-project/issues/81911.