KVM: riscv: selftests: Add smstateen registers to get-reg-list test

We have a new smstateen registers as separate sub-type of CSR ONE_REG
interface so let us add these registers to get-reg-list test.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Anup Patel <anup@brainfault.org>