[Pallas] Fix shard_axis in dma_start interpret mode rule.

PiperOrigin-RevId: 703249904

Author: justinjfu

jax/_src/pallas/mosaic/primitives.py

@@ -615,7 +615,7 @@ def dma_start_discharge_rule(in_avals, out_avals,
       if device_id_len > 1 or len(nonempty_axes) > 1:
         raise NotImplementedError("Meshes with more than 1 named dimension not "
                                   "implemented in dma_start_p")
-      shard_axis = nonempty_axes[0].name
+      shard_axis = nonempty_axes[0]
       my_axis = jax.lax.axis_index(shard_axis)
     else:
       raise ValueError(f"Unknown device_id_type: {device_id_type}")