KVM: riscv: selftests: Selectively filter-out AIA registers

Currently the AIA ONE_REG registers are reported by get-reg-list
as new registers for various vcpu_reg_list configs whenever Ssaia
is available on the host because Ssaia extension can only be
disabled by Smstateen extension which is not always available.

To tackle this, we should filter-out AIA ONE_REG registers only
when Ssaia can't be disabled for a VCPU.

Fixes: 47706939

 ("KVM: riscv: selftests: Add get-reg-list test")
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Anup Patel <anup@brainfault.org>