[SYCL-MLIR] Add back the reverted sycl commit

[whitneywhtsang]

• Revert the revert of "[NFC][SYCL] Replace #pragma unroll with dim_loop in accessor.hpp ([NFC][SYCL] Replace #pragma unroll with dim_loop in accessor.hpp #6939)"
• Update supportedFuncs for single_task.cpp.

Note: Do not squash and merge.

[sommerlukas]

LGTM.

Do I understand correctly that the runtime error was caused by a function not being emitted because it was not in the list of supported functions yet?

[whitneywhtsang]

Do I understand correctly that the runtime error was caused by a function not being emitted because it was not in the list of supported functions yet?

That's correct.