[OpenCL] Fixes device name comparison stage_op_test (#10760)

* [OpenCL] Fixes device name comparison stage_op_test

Changes the fixed '/device:GPU:0' expected device name string to the
name returned by 'test/gpu_device_name()', as the device name could be
'/device:SYCL:0' or '/device:GPU:0'.

* [OpenCL] Fixes testing of CUDA device name

The CUDA device name reported by test_util is in the form '/gpu:0',
while the device name used in the nodes looks like '/device:GPU:0'. When
running on CUDA we need to change the expected device name accordingly,
however this isn't a problem on SYCL.