[mlir][gpu] Relax restriction on MMA store op to allow chain of mma ops.
In order to allow large matmul operations using the MMA ops we need to chain
operations this is not possible unless "DOp" and "COp" type have matching
layout so remove the "DOp" layout and force accumulator and result type to
Added a test for the case where the MMA value is accumulated.
Differential Revision: https://reviews.llvm.org/D103023