target/riscv: Support setting external interrupt by KVM

target/riscv: Support setting external interrupt by KVM

When KVM is enabled, set the S-mode external interrupt through
kvm_riscv_set_irq function.

Signed-off-by: Yifei Jiang <jiangyifei@huawei.com>
Signed-off-by: Mingwang Li <limingwang@huawei.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>
Message-id: 20220112081329.1835-8-jiangyifei@huawei.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>