sycl: add REPEAT_BACK operation support (llama/16734)

sycl: add REPEAT_BACK operation support (llama/16734)

* SYCL repeat_back v1 — add core op + switch case

* Implement repeat_back SYCL operation and minor fixes

* Update ggml/src/ggml-sycl/repeat_back.cpp

Co-authored-by: Sigbjørn Skjæret <redacted>
* Update ggml/src/ggml-sycl/repeat_back.hpp

Co-authored-by: Sigbjørn Skjæret <redacted>
* Update ggml/src/ggml-sycl/ggml-sycl.cpp

Co-authored-by: Sigbjørn Skjæret <redacted>
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Co-authored-by: Sigbjørn Skjæret <redacted>