Fix the memory space attribute for new allocation

[yzhang93]

• Previously, the new allocations are always set as AMDAIEMemSpace::Local, since the others have already be bufferized with the correct memory space before comprehensive-bufferization. However, for the newly added test case, there's truncf op to convert f32 back to bf16. The previous memref allocation data type in L2 is f32, so we'll need a new allocation with data type bf16 in L2 memory space. This PR fixed such problem which had the wrong memory space.