[mlir][vector] Relax transfer_read/transfer_write restriction on memref operand

Relax the verifier for transfer_read/transfer_write operation so that it can
take a memref with a different element type than the vector being read/written.

This is based on the discourse discussion:
https://llvm.discourse.group/t/memref-cast/1514

Differential Revision: https://reviews.llvm.org/D85244