KVM: riscv: selftests: Add senvcfg register to get-reg-list test

We have a new senvcfg register in the general CSR ONE_REG interface
so let us add it 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>