[mlir][NVGPU] Validate mmaShape has 3 elements in MmaSyncOp/MmaSparseSyncOp (#190928)
Add validation in MmaSyncOp::verify and MmaSparseSyncOp::verify to
ensure `mmaShape` contains exactly 3 elements before calling
getMmaShapeAsArray() to avoid crash. Fixes
https://github.com/llvm/llvm-project/issues/173378.