[SYCL][Doc] Update restrictions in extension

[gmlueck]

Update the description of the limitations in the
"sycl_ext_oneapi_device_architecture" extension. The newly added host APIs in that extension do not have the same restrictions as the if_architecture_is function.

[gmlueck]

@dm-vodopyanov are there any other restrictions we should capture for this extension? For the new host-side APIs, do they work with all backends or only with Level Zero?

[dm-vodopyanov]

@dm-vodopyanov are there any other restrictions we should capture for this extension? For the new host-side APIs, do they work with all backends or only with Level Zero?

Currently host-side APIs work for Level Zero and OpenCL backends only, and so only Intel GPU architectures are covered.
There might be a limitation related to querying CPU architectures: we currently report that the architecture is just x86_64, we don't specify the exact CPU architecture like SKL, SPR, etc.
For device-side APIs, no other restrictions.

[gmlueck]

Currently host-side APIs work for Level Zero and OpenCL backends only, and so only Intel GPU architectures are covered.
There might be a limitation related to querying CPU architectures: we currently report that the architecture is just x86_64, we don't specify the exact CPU architecture like SKL, SPR, etc.

Thanks. I noted the limitations with Nvidia and AMD devices in f97f299.

I think the CPU issue you describe does not need to be noted as a limitation because the current API does not provide any way to get more detail about the CPU device architecture. We might decide to add this granularity in the future, but for now it is not part of the extension.