target/riscv: Create an KVM AIA irqchip

target/riscv: Create an KVM AIA irqchip

We create a vAIA chip by using the KVM_DEV_TYPE_RISCV_AIA and then set up
the chip with the KVM_DEV_RISCV_AIA_GRP_* APIs.
We also extend KVM accelerator to specify the KVM AIA mode. The "riscv-aia"
parameter is passed along with --accel in QEMU command-line.
1) "riscv-aia=emul": IMSIC is emulated by hypervisor
2) "riscv-aia=hwaccel": use hardware guest IMSIC
3) "riscv-aia=auto": use the hardware guest IMSICs whenever available
                     otherwise we fallback to software emulation.

Signed-off-by: Yong-Xuan Wang <yongxuan.wang@sifive.com>
Reviewed-by: Jim Shu <jim.shu@sifive.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Message-ID: <20230727102439.22554-4-yongxuan.wang@sifive.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>