[NFCI][CodeGen, AArch64] Fix inconsistent TargetCostKind types.

The pass uses different cost kinds to estimate "old" and "interleaved" costs:
default cost kind for all targets override `getInterleavedMemoryOpCost()` is
`TCK_SizeAndLatency`. Although at the moment estimated `TCK_Latency` costs are
equal to `TCK_SizeAndLatency`, (so the change is NFC) it may change in future.

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D110100