[llvm] [NFC][TTI] Remove default CostKind from TTI::getMemoryOpCost() (PR #219070)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon approved this pull request.

LGTM - although LowerMatrixIntrinsics seems to be inconsistent with using the common CostKind and explicit TTI::TCK_RecipThroughput in its cost calls

https://github.com/llvm/llvm-project/pull/219070