downcast MiniMax-H3 position_ids at the device transfer on fp64-less backends (#14767)

Both layout steps build position_ids in float64 on CPU and then move it to
the execution device with a plain .to(device), which raises on MPS. Pass the
dtype through maybe_adjust_dtype_for_device so the transfer lands as float32
on mps/npu/neuron and is unchanged everywhere else. The fp64 construction is
untouched, and MiniMaxH3RotaryPosEmbed.forward already casts position_ids to
float32, so no device sees different rotary angles.

Co-authored-by: Sayak Paul <spsayakpaul@gmail.com>