target/riscv: Expose the Smcntrpmf config

target/riscv: Expose the Smcntrpmf config

Create a new config for Smcntrpmf extension so that it can be enabled/
disabled from the qemu commandline.

Signed-off-by: Atish Patra <atishp@rivosinc.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20240711-smcntrpmf_v7-v8-13-b7c38ae7b263@rivosinc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>