target/riscv: read marchid/mimpid in kvm_riscv_init_machine_ids()

target/riscv: read marchid/mimpid in kvm_riscv_init_machine_ids()

Allow 'marchid' and 'mimpid' to also be initialized in
kvm_riscv_init_machine_ids().

After this change, the handling of mvendorid/marchid/mimpid for the
'host' CPU type will be equal to what we already have for TCG named
CPUs, i.e. the user is not able to set these values to a different val
than the one that is already preset.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20230706101738.460804-8-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>