[mlir][spirv] Clean up SPIRVOps.cpp. NFC.

Resolve almost all clang tidy warnings in this file:
1. Clean up string constants.
2. Use consistent argument names across function declarations and definitions. Rename `state` - > `result`, which is consistent with the other dialects.
3. Remove misleading function parameter name comments (`argTypes`). This did not match the actual function argument (`bool enableNameShadowing`).
4. Simplify calls to `is_splat`.

Reviewed By: antiagainst

Differential Revision: https://reviews.llvm.org/D131297