Fix verification of zero-dim memref in affine.load/affine.store/std.load/std.store

Fix verification of zero-dim memref in affine.load/affine.store/std.load/std.store

Verification complained when using zero-dimensional memrefs in
affine.load, affine.store, std.load and std.store. This PR extends
verification so that those memrefs can be used.

Closes tensorflow/mlir#58

COPYBARA_INTEGRATE_REVIEW=https://github.com/tensorflow/mlir/pull/58 from dcaballe:dcaballe/zero-dim 49bcdcd45c52c48beca776431328e5ce551dfa9e
PiperOrigin-RevId: 262164916