[mlir][affine] Remove one-element linearize_index as a canonicalization (#115542)
By analogy to the canonicalization for affine.delinearize_index, remove
affine.linearize_index ops that only have one multi-index input.
Example:
Canonicalize
```mlir
%1 = affine.linearize_index [%0] by (64)
```
to
```mlir
%1 = %0
```
While I'm here, get rid of an extra space in the syntax.