KVM: arm64: vgic: Reset in_kernel on private IRQ allocation failure

kvm_vgic_create() sets vgic.in_kernel before allocating the per-vCPU
private IRQs, but the allocation-failure path resets only vgic_model and
leaves in_kernel set. As irqchip_in_kernel() is !!in_kernel, the VM is
left with an in-kernel irqchip but no model, and the -EEXIST guard at the
top of kvm_vgic_create() rejects every retry, so userspace cannot recover
from a transient -ENOMEM.

Reset in_kernel alongside vgic_model on the failure path.

Fixes: 9435c1e143 ("KVM: arm64: gic: Set vgic_model before initing private IRQs")
Cc: stable@vger.kernel.org
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://patch.msgid.link/20260802150845.3485757-1-fuad.tabba@linux.dev
Signed-off-by: Oliver Upton <oupton@kernel.org>

arch/arm64/kvm/vgic/vgic-init.c

@@ -176,6 +176,7 @@ int kvm_vgic_create(struct kvm *kvm, u32 type)
 		}
 
 		kvm->arch.vgic.vgic_model = 0;
+		kvm->arch.vgic.in_kernel = false;
 		goto out_unlock;
 	}