fix sycl.h deprecation warnings

[brianwhitney59]

With the upcoming Intel oneAPI 2026.0 release, the deprecations warnings will now be errors. The file include/gt-fft/backend/sycl.h needs to be updated. Attached is an updated file that addresses this issue. These changes work with release 2025.3, and the changes are guarded to reflect that.

For the test that I ran, this version of sycl.h worked for oneAPI 2025.2.0, oneAPI 2025.3.0 and an internal version of oneAPI 2026.0.0.

sycl.h.txt

[bd4]

Thanks for the heads up, I will integrate this as soon as the release is public.