target/riscv/kvm: add missing KVM CSRs

target/riscv/kvm: add missing KVM CSRs

We're missing scounteren and senvcfg CSRs, both already present in the
KVM UAPI.

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: <20250224123120.1644186-4-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>