target/riscv: pmp: exit csr writes early if value was not changed

target/riscv: pmp: exit csr writes early if value was not changed

Signed-off-by: Loïc Lefort <loic@rivosinc.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: LIU Zhiwei <zhiwei_liu@linux.alibaba.com>
Message-ID: <20250313193011.720075-5-loic@rivosinc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>