target/riscv: Remove check on RVH for riscv_cpu_set_virt_enabled

target/riscv: Remove check on RVH for riscv_cpu_set_virt_enabled

In current implementation, riscv_cpu_set_virt_enabled is only called when
RVH is enabled.

Signed-off-by: Weiwei Li <liweiwei@iscas.ac.cn>
Signed-off-by: Junqiang Wang <wangjunqiang@iscas.ac.cn>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: LIU Zhiwei <zhiwei_liu@linux.alibaba.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20230327080858.39703-5-liweiwei@iscas.ac.cn>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>