target/riscv: cpu: Remove compile time XLEN checks

target/riscv: cpu: Remove compile time XLEN checks

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Bin Meng <bin.meng@windriver.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
Acked-by: Palmer Dabbelt <palmerdabbelt@google.com>
Tested-by: Bin Meng <bin.meng@windriver.com>
Message-id: a426ead44db5065a0790066d43e91245683509d7.1608142916.git.alistair.francis@wdc.com