[Flang] Add Minloc to simplify intrinsics pass

This patch adds minloc to the simplify intrinsics pass, supporting calls with KIND or MASK arguments while calls which have BACK, DIM or have a CHARACTER input array are rejected. This patch is targeting exchange2, and in benchmarks provides a ~11% improvement in performance.

Also included are some minor style changes / cleanup in simplifyIntrinsics.cpp.

Reviewed By: vzakhari

Differential Revision: https://reviews.llvm.org/D144103