[fir][NFC] Remove fir.cmpf replaced by mlir.cmpf

fir.cmpf op is not necessary anymore as it is replaced by mlir.cmpf.
This patch is part of the upstreaming effort from fir-dev branch.

Reviewed By: jeanPerier

Differential Revision: https://reviews.llvm.org/D110327

Co-authored-by: schweitzpgi
Co-authored-by: jeanPerier