[SYCL] Use consistent DeviceType across different environment variables

[uditagarwal97]

Is your feature request related to a problem? Please describe

For ONEAPI_DEVICE_SELECTOR, DeviceType is cpu, gpu, fpga
For SYCL_DEVICE_ALLOWLIST, DeviceType is cpu, gpu, acc, fpga
For SYCL_REDUCTION_PREFERRED_WORKGROUP_SIZE, DeviceType is cpu, gpu, acc.

There's inconsistency in the DeviceType value accepted by different environment variables.

Describe the solution you would like

Ideally, we should reconcile the discrepancy in DeviceType and use a consistent terminology for all the environment variables.

Describe alternatives you have considered

No response

Additional context

No response