RISC-V: KVM: Check host Ssaia extension when creating AIA irqchip

RISC-V: KVM: Check host Ssaia extension when creating AIA irqchip

The KVM user-space may create KVM AIA irqchip before checking
VCPU Ssaia extension availability so KVM AIA irqchip must fail
when host does not have Ssaia extension.

Fixes: 89d01306e34d ("RISC-V: KVM: Implement device interface for AIA irqchip")
Signed-off-by: Anup Patel <anup.patel@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20260120080013.2153519-4-anup.patel@oss.qualcomm.com
Signed-off-by: Anup Patel <anup@brainfault.org>