[SYCL] Fixed minor bug when enabling FP16 for non intel targets (#6464)
* moved INTEL_MKL guard from gemm_impl to gemm (wrapper)
* Update ggml-sycl.cpp
Co-authored-by: AidanBeltonS <87009434+AidanBeltonS@users.noreply.github.com>
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Co-authored-by: AidanBeltonS <87009434+AidanBeltonS@users.noreply.github.com>