We do not need to schedule another loop interchange pass after Polly, as Polly

should perform loop interchanges itself.

This also fixes a bug we see due to the "loop-interchange" pass producing
incorrect IR when compiling linpack-pc.c from the LLVM test-suite with
"-polly-position=before-vectorizer".

Reviewed-by: Tobias Grosser <tobias@grosser.es>
llvm-svn: 257495