check to_copy args in vulkan_partitioner (#6215)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/6215

in exir dialect, to_copy doesn't have dtype arg and it is inferred from the dtype of the output tensor. The args will be of length 1 with the sole arg being the input tensor. Thus the previous check always returns False as args is never > 1.

Reviewed By: SS-JIA

Differential Revision: D64267104

fbshipit-source-id: 62267ecae167aef7ecc415bf83f1fb024d66244f