[opt] Exposing the parameters of LoopRotate to the -passes interface

There is a gap between running opt -Oz and running opt -passes="OZ_PASSES" where OZ_PASSES is taken from running opt -Oz -print-pipeline-passes.

One of the reasons causing this is that -Oz uses non-default setting for LoopRotate but LoopRotate does not expose its settings when printing the pipeline.

This commit fixes this by exposing LoopRotates parameters.

Reviewed By: aeubanks

Differential Revision: https://reviews.llvm.org/D153437