Target options for PULP RISC-V GNU Compiler Toolchain

[zhoutianyang]

For new toolchain @ https://github.com/pulp-platform/riscv-gnu-toolchain,
I am trying to build a toolchain for RI5CY, but got a warning when using -march=rv32imfcxpulpv2

cc1: warning: '-march=rv32imfcxpulpv2': m (multiplication) extension is enabled with pulpv2. This was originally not allowed

What's the correct option for RI5CY?