When any of the memrefs in a structured linalg op has a zero dimension, it becomes dead.
This is consistent with the fact that linalg ops deduce their loop bounds from their operands.
Note however that this is not the case for the tensor<0xelt_type> which is a special convention
that must be lowered away into either memref<elt_type> or just elt_type before this
canonicalization can kick in.