[Flang][MLIR][OpenMP] Add support for logical eqv in worksharing-loop

The patch adds the lowering from Flang parse-tree to FIR+OpenMP. The
conversion code is also added in MLIR.

Reviewed By: kiranchandramohan

Differential Revision: https://reviews.llvm.org/D133442



Co-authored-by: Kiran Chandramohan <kiran.chandramohan@arm.com>