[MLIR][normalize-memrefs] Non-normalizable operations with identity map...

[MLIR][normalize-memrefs] Non-normalizable operations with identity map layouts do not block normalization of the entire function

The current approach is convervative in which whenever there is a
non-normalizable operations in a function will the function be labelled
as non-normalizable. It means it requires that all operations must have
MemRefsNormalizable trait.

This patch relaxes the requirement that if the memref map layouts of a
non-normalizable operation are identity, this operation does not block
the normalization of the other operations in the same function.

Reviewed By: bondhugula

Differential Revision: https://reviews.llvm.org/D125854