Remove simplification rule that could cause infinite loops.
Remove simplification rule that could cause infinite loops.

Closes #338.

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