[mlir][AMGPU] Replace use of SmallVector with ArrayRef, NFC (#163770)
Improving choice of class used, from SmallVector to ArrayRef
(https://llvm.org/docs/ProgrammersManual.html#llvm-adt-arrayref-h). Also infer template types when possible.
Leftover from https://github.com/llvm/llvm-project/pull/155951.
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Signed-off-by: Muzammiluddin Syed <muzasyed@amd.com>