[AVR] Remove earlyclobber from LDDRdPtrQ (#85277)
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:
https://github.com/llvm/llvm-project/blob/a99b912c9b74f6ef91786b4dfbc25160c27d3b41/llvm/lib/Target/AVR/AVRInstrInfo.td#L1421
Closes https://github.com/llvm/llvm-project/issues/81911.
