[Polly][OpTree] Fix mid-processing change of access kind.

Operand tree forwarding can cause the change of an access kind; in
particular change from a scalar kind to an array kind if the scalar
dependency is not necessary. Such an access cannot and doesn't need to
be forwarded anymore.

Fixes llvm.org/PR48034

GitOrigin-RevId: c8a0e27cfb8311cdacbc6509cb3a7bf4e055affd
2 files changed