[llvm] [RISCV] Implement RISCVTTIImpl::getPreferredAddressingMode for HasVendorXCVmem (PR #120533)

[Philipp van Kempen via llvm-commits]

PhilippvK wrote:

@wangpc-pp Thanks to your hint, I could reduce the complexity of the test case: https://github.com/llvm/llvm-project/pull/120533/files#diff-ef5be54f9e88c12d2f5283d2cf71802e3ccdfbe601f89c0e8c2d9eda7c01a986

https://github.com/llvm/llvm-project/pull/120533