Fix exotic fusion bug.
Fix exotic fusion bug.

We should only apply transformations to the inputs that are actually
involved in the fusion operation.

ihc/futhark,ihc/futhark,diku-dk/futhark,HIPERFIT/futhark,diku-dk/futhark,ihc/futhark,diku-dk/futhark,HIPERFIT/futhark,diku-dk/futhark,diku-dk/futhark,HIPERFIT/futhark