'Crossing ways' shouldn't include grade separations

[NE2]

The 'crossing ways' validation would be a lot more useful if it didn't list cases where one of the following is true:
*Only one of the ways is a bridge or tunnel, or one is a bridge and the other a tunnel
*Both ways are bridges or tunnels, and the layer values are different
In other words, it would still list cases of bridges or tunnels crossing where the layer values are the same or one or both are not set.